Sibling's(26F) first ever relationship is with a newly-divorced man (46M) with a 20 year age gap. Are my concerns warranted? Should I tell her?

Hello all. This will likely be a throwaway account.

I don't know where else to post, as I feel this is most relevant to this subreddit. Apologies if it is not.

TLDR: My sibling (26F) is in her very first relationship with a newly divorced man (46F) that is 20 years older than her, and he is her former boss's ex-husband. They all knew one another before the divorce, and still do after, and her former boss works in the same department as her. Aside from the obvious massive age gap and first time relationship, I think there are a lot of red flags about this relationship that put me at unease for her sake and her future. Am I just being an overprotective sibling, or are my concerns warranted?

So here's all the details if you're into a long read, as I think the details are necessary.

Throwaway account. I just need to know that I'm not being an insane overprotective sibling, because everything about this relationship just puts me at unease, and has a lot of questionable things. I barely slept after they told me, and I am very anxious over it, to the point of being sick. I just need to know if I'm overreacting or not. Please read the whole thing before commenting. I feel the details are necessary to understand where I'm coming from. I'm fine being wrong, which is why I want to hear others opinions once they've had the chance to digest the situation, as I have. I purposely refrained from posting for at least a day or two to try and process in my own head what was going on, to prevent being reactionary. 

It's there in the title. My sibling is in their very first relationship, but it has a very large age gap. 20 years to be exact. My sibling is in her mid to later 20s, and the partner is in their 40s, newly divorced (sounds like it's not quite finalized, but very close to it), and they've been hiding it from me and everyone for months, at least 5+ it sounds like. My sibling and I are very close, we're twins, so the fact that she hid this from me for months now, and I am the only one she told, tells me deep down she knows this is probably wrong (though maybe I'm reading into it too much). She has not told anyone except for me, and I am not going to tell anyone either, since she asked. I want to be respectful of her wishes, and don't want to break her trust. I want to let her be the one to let our family and mutual friends know, since that is what she wants, even if it takes a few more months of hiding it. 

Aside from the fact that this is her first relationship (that I know of- again, we are very close, literally shared the same womb and room), and the age gap is very large, there are other details that have me even more concerned. 

-The man is newly divorced. It sounds like he is not quite, quite finalized with it, but it's very close according to her. The split was supposedly amicable with the former wife, they just grew apart. I have met both the former wife and this man before, since I would go down to visit my sister at her job, she introduced me to both.

-The former wife of this man, is my sister's former boss, who she worked for/with for around 5 years, in two different locations. 

-Although the former wife is no longer my sister's boss, and they live and work 400+ miles apart, they do work at the same university, with ties to the same people in the same department. 

-The department they both work for at the University is known to be extremely gossipy. Can confirm because my sister and I went to the same university, and although I was not in the same major as her, most of our mutual friends and her were in that major with ties to that department, so I heard a lot about his gossip-y it is. 

-I know that my sister is financially vulnerable, and has been for a long time (though who isn't in this economy?). I have lent her thousands of dollars to help her out over the last few years, even when I couldn't truly afford to since I'm also a recent grad, with no real expectations of her paying me back, because that's what you do when you care about someone. I worry that her financial stress and situation (she had to take out a ton of predatory payday loans to move to her former work location and afford her old apartment where she worked with the man's former wife) may make her vulnerable, in that she's so stressed, that any sort of comfort and relationship at this time she would welcome, and ignore any red flags. While I don't *think* the man is paying for ANYTHING for her, so it's not a sugar baby situation, I think just the stress of being not even paycheck to pay check may make her overlook red flags. Additionally, she for the last few years has worked regularly 6-7 days a week, usually 70+ hours a week at three to four different jobs just trying to make ends meet and pay off debt, including selling blood plasma to the point of scarring. She has had no time to actually date and meet people, and see what she likes and doesn't, other than who she sees at work ... which would be this man ... since he was her former boss's former husband. I feel I'm not working this bullet very effectively, but hopefully everyone sees my drift. TLDR: she is so financially stressed and works so much that she literally doesn't have time to date, so the only contact with a man she has truly had, has been the former boss's husband. I know she doesn't have the time, because again, we are close, and I lend her money a lot, and hear about all her gigs. 

-We both are estranged from our father. Our father was quite abusive financially, emotionally, and sometimes, physically, to our mother growing up. He was enormously depressed after the '08 financial crisis, and started using drugs, mainly abusing prescriptions, but some cocaine too. Our brother was also physically abused at points, to which I had to physically attack my dad to try to get him off my brother. I am the oldest sibling. I am very protective, be it physically, emotionally, and financially over my siblings, as I feel I have to be. There was an extremely contentious divorce, and it affected all of us, whether we talk about it or not. I have been in therapy and on medication for years trying to deal with the after effects of witnessing, and experiencing at least the emotional abuse. I don't know if my sister has, but I do question if she has the same struggles with being witness to all that, and estranged, as I do. I'm not trying to say she has daddy issues, or that I do, but it's hard not to factor it into the equation, given my own struggles, and seeing as we witnessed the same things (or at least I think we did. I again feel very protective as the oldest, and would often try to break up my dad when he was fighting or being an ass). 

My mind is so frayed and worried right now, that I think I'm honestly missing a bunch of things. While I don't think the guy has any malicious intent, I've met him once at her work and he seemed kind at least, I also really don't truly know him. 

To state the obvious, this man is in a very different phase of life than her. He's been married and now divorced before, he's bought a house, has a well established business, and from what I can tell, isn't paycheck to paycheck like she is. She is just starting a new job, still trying to make ends meet, I am still helping her out financially from afar (I moved states with my now husband about 1.5 years ago), still working insane hours, she has never had a previous relationship, and is still just trying to pay off debt, figuring out what she wants in a career, and has hopes to one day buy a house when she can. She at the very least, I will give her credit, stated she would not want to move in with him until she gets her financial situation sorted out, and the divorce is completely final. 

I also very much worry since she was previously good friends with her former boss (again, this man's former wife), knew her closely, literally petsat for her a ton while in college and working at the same facility, that this may come to bite her in the ass if the ex-wife finds out. While my sister and her boss work in two separate facilities now 400+ miles apart, they still work for the same university, for the same overhead department. Although there was never any funny business going on between my sister and the man while the former boss and the man were married, and this only started after they divorced and separated, I can't help but think and worry that this woman, her former boss, will start to wonder "Were they messing around right under my nose, and that's what drove me and my now ex-husband apart?" given the proximity of the three of them. They all knew one another when the two were still married, and they all still know one another as they finalize their divorce, and my sister is now involved with the man. It would be hard, personally, for myself not to wonder that question if this same situation happened, given the proximity of everyone, so I question if the ex-wife/former boss  will wonder this. If she does, given that she and my sister work in the same department, and it is very gossipy, how does that then play out? I don't think it's any stretch of the imagination that even if the ex-wife simply shared her concerns with a coworker, that it wouldn't make the rounds around the department, and result in my sister being known as "the other woman," even if there was NEVER any cheating involved. If that rumour got out about her, even if not true, I think it would be extremely hard to then try and promote, or move to different jobs within the department (which she very much wants to do), with that sort of rumour following you. I think it would spell disaster for her career, given that the university and the department is world-renown, and one of the only places she's ever going to get a job in theat pays decently, since her work is more specialized. To add even more fuel to the potential fire - most of her former coworkers also know this man, since again, he was at the ex-wife's work a fair amount, just given his line of work. I really don't think it's a stretch to say rumours could be set aflame, and her reputation would be damaged. 

I've spent an hour+ thinking and typing this up. I apologize for it's length, but I just needed to put all the details in there for my own sake as well, since writing things out I think helps me process. I very much worry that she is insanely blinded by heavily  rose-tinted  glasses, and can't see a lot of the red flags that I am seeing. It being her first relationship in her mid-late twenties, and she's financially stressed, I also wonder if there is an element in there of being just desperate and wanting to have a relationship for the first time, and be with a man. I can certainly understand that viewpoint, as I felt that way since I also didn't have a relationship for the first time until my mid twenties - I felt a little dedparate at points. 

I'll stop before I continue to ramble, but yeah. I just need to know if others are seeing the same red flags that I am, in addition to the obvious: the insanely large age gap. I don't even need to dive into the complexities of the age gap like a partner dying 20-30+ years before you do, becoming your partners caretaker when they age before you do, etc. I've already considered those points since I'm a long-term thinker, and this prospects trouble me as well. 

I very much want to see my sister find love, be happy, and enjoy a relationship - I just think that this one has caution tape all over it.