AITA for Destroying Hope for a Family Get-Together

TLDR: my sister was discovered to have been stealing large amounts of cash from my mother over a series of years, and now I'm being made to feel like I'm the A-hole on my dad's side because I refuse to be at Christmas dinner with her accomplice until there's an apology. 

I know you like 'em long and chunky, Charlotte, so this one's for you.

My sister, let's call her Heather, has had a problem with stealing ever since she was little. I didn't know anything about it until we were older. The first I knew was when we were at my mother's friend's place, let's call her Cindy. My mother and Cindy had that kind of relationship where the kids frequently stayed at each other's houses in various combinations. Pretty much an open door policy between the two families. One day, Cindy and my parents and Heather spent hours in the basement having some kind of serious discussion. I didn't find out until years later that they were confronting Heather over having discovered that she had been stealing jewelry and money out of everyone's bedrooms at Cindy's house. Heather was only about 9 years old or so at this point. No matter how many times they asked, told her that she's making it worse for herself by not telling them where the items are, or reminding her that she had been caught red-handed, she refused to acknowledge fault or even talk about it at all. As far as I know, the items were never recovered.

Years went by, and it became something of a game in our house. I would spot my belongings in Heather's room as I passed the open door, I would take them back, and she'd accuse me of being the bad buy for going into her room without asking.

Like anyone, Heather's not all bad. In fact, I was out of the country when we found out that my mother was in an abusive relationship. Heather was the one who rallied to get my mother out of there and set up in an apartment across the hall. IN time, my mother moved from that apartment to a house where she ran a cash business and did very well for herself. It was at this house that my mother was hosting some people in the backyard with Heather and her girlfriend present (let's call the girlfriend Loopy). 

My mother got up to go inside for a moment and left her purse hanging on the back of her chair. One of my mother's work colleagues thought it was weird that Loopy got up and moved into my mom's seat. Then the colleague noticed that Heather was standing behind the chair, reaching into my mother's purse and removing cash. They were so brazen about it that they were discussing which denomination of bills to take and which to leave, in earshot of everyone. My mother's work colleague got up, went into the house, and brought to my mom's attention what she had just seen. My mother called Heather into the house and told her she had been caught. My sister tried to laugh it off, then gathered her things with Loopy and left in a big hurry.

That's when my mother put two and two together. When she first started to notice that her neat $1000 stacks of cash from her business that she hid in her bedroom were missing $200-300 at a time, she thought she had counted wrong. Then it clicked. 

For years it was a regular thing that Heather would drop into my mother's house, say that she happened to be in the neighborhood, and that she really had to go to the bathroom. She would go upstairs, do her business, and then leave in an awkward hurry. When my mother shared her hunch about what was happening to the cash with my younger sister (let's call her Angela), Angela mentioned that she thought it was weird one time when she caught Heather in Mom's bedroom during one of these drop-in bathroom visits. 

Heather has never been good about her personal finances. She and Loopy both make good money as supervisors at their workplace (they work together too), but they spend everything as fast as they earn it, leaving a trail of bad debt, unpaid bills, and stolen merchandise in their wake. They constantly borrowed money from anyone who would give it to them, and asked my Mother for handouts constantly.

I didn't know about any of this until it all blew up but there had been a pattern of behaviour over years with Heather making charges to my mother's credit card and never paying for it, or borrowing her car for days or even weeks at a time without bringing it back. 

I'm trying to paint a picture here of my sister kind of walking around thinking that she's entitled to everything that belongs to everybody else, having no sense of how her actions impact anybody else, and abusing my mother over a long period of years. She even got mad at my Dad when he bought a sailboat, saying that he should have given that money to his kids. 

But it had nothing to do with money when Loopy's teenage son stole my mother's car and went joyriding. My mother got the police involved, but Heather called the police, impersonated my mother, said that she had changed her mind and didn't want to pursue it, and asked to have the charges dropped. 

So this whole thing with stealing cash was kind of, finally, a last straw. The problem though is that my sister has some kind of mental or emotional problem with this stuff where she either can't or refuses to talk about it. We all knew about it. It was all out in the open. But if you tried to talk to her about it, she would just stonewall you. She would literally sit there, unresponsive, until you tired yourself out.

My parents divorced when us kids were young, so my Father wasn't really privy to any of what was happening. In fact, my dad grew up quite sexist and treated my sister differently than me, and I think he feels guilt about how she turned out. So he and my sister very much had a daddy's little girl relationship once she was an adult. She would never try anything like what she does to our mother with him. 

The Autumn after the stealing cash thing had blown up, my father and stepmother announced that they were taking all of the adult kids on a tropical all-inclusive resort vacation over Christmas. I told them to put me in a room with Heather, thinking that the proximity would give us ample time to discuss what had gone on. Once we were alone in the room together, I brought it up. She said that she wasn't going to talk about it with a smug, arrogant attitude. It was almost like she was proud that I couldn't get her to talk. 

I tried to explain to her that this is the kind of thing that creates fractures that people never get over for the rest of their lives. That right now is our moment to save the relationship. And she went the other way with it, insisting that I was the bad guy for bringing this up on our family trip. She thought I was going to make it a focal point of the trip and talk about it with the family the following day. I told her that I wasn't going to bring it up and I wouldn't let it ruin the trip for everyone, but that she had to know she was risking her relationship with me, and perhaps even with her mother, by refusing to talk about what had happened. I guess she was okay with that because we didn't talk about it anymore, and that was the end of that. 

Imagine how horrified I was at the end of the trip when we arrived to the airport to find Loopy there to pick her up. I wanted to barf, and I wanted to punch her. These people literally have no shame. 

In time, my sister shocked us all when she shared with the family that she was leaving Loopy and moving out on her own. She had still not acknowledged anything that had happened or made any attempt at apology or reconciliation, but this was a start. She was out of that home for only a month or two before she went back, saying that no one was supporting her, and at least Loopy accepted her for who she was. 

On account of how my father treated her, my mother swung wildly to the other direction and never held Heather to account for her actions all along the way when she was a kid. After my parents' divorce, my mother frequently talked about Heather and my Father as if his emotional neglect was a defining characteristic. My mother feels a tremendous amount of guilt for who Heather turned into, for the fact that my mother so coddled Heather as a child. 

That was also part of the reason why my Mother couldn't bear to cut Heather off after everything that had happened. My sister reached out to my mother to go for coffee here and there, little visits and phone calls. When their relationship had reached a new level of calm, Heather asked Mom if she could rent a car for the weekend, put it on Mom's credit card, and give Mom the cash. 

They went to the rental place to get the car, and Heather said she had forgotten the cash, but they could swing by her place to get it on the way home. After they got the car, my sister remembered she was in a big hurry and asked if she could bring the cash by later. She never did. And in fact, the next thing my mom heard about it was two weeks later, when the car rental place called to ask when the car was coming back, threatening to sue.

My mother called me to tell me what had happened, and I broke down in tears because that was when I realized there would never be a resolution. My sister was absolutely degenerate in her tendency to steal, staunchly refuses to change, and will hurt anyone who gives her the slightest opportunity.

Heather still calls to invite Mom for coffee and whatnot, but Mom does not accept the invitations. She has reached the point where she will never know whether her daughter actually wants to see her, or is just buttering her up to ask for money or steal again. It's kind of tragic.

Fast forward to my wedding coming up. I called my sister on the phone to tell her that she's family, unconditional love and all of that, she's welcome at my wedding,  but Loopy is not. Heather threw an absolute fit, called me all kinds of names, and did not attend the wedding. Of course, I'm the bad guy for not accepting her partner.

And now we get to the whole thing that this post is about. My father and stepmother moved into a new, beautiful home in the country and wanted to do a big holiday dinner for all of the kids, most of whom are now married with kids of their own. It was going to be a beautiful occasion, except that I put my foot down that I can't sit at the holiday dinner table and make nice with Loopy without some attempt at reconciliation. My sister got on the phone with me and told me off, told me I was ruining Christmas. My dad even got me on the phone and tried to reason with me about letting things slide for the sake of the holiday. I brought him up to speed and told him about all of the things that had happened all along the way. I even made clear that I would be willing to spend time with these people if there was any recognition of what happend and an honest attempt at reconciliation. But this is what they do: lay low until enough time has gone by that everyone around them is willing to be polite for the sake of appearances, and then strike again when the guard is down. 

Now the family, and even the extended family of aunts and uncles and whatnot, feel like there can never be another large family get-together, and that I am the reason why. I'm kind of hurt and offended that my father seems to want to ignore my sister's problems and sweep everything under the rug for the sake of playing nice, but I feel like no one is sticking up for my mother in this scenario. So there you go. Am I the asshole?