Feelings for straight colleague.

Hi all - looking for advice for what seems to be an impossible (though not unique) situation. Will try not to make this too long. TLDR: I’ve fallen for a straight friend and colleague, I’ve realized I have no chance with her but also can’t tell her or build any real distance between us, so need to privately get over it.

By way of background, I (35F) am somewhere between bi and gay. I’ve struggled immensely with my sexuality - including figuring it out - my entire life to the point that I’ve never had any lasting truly meaningful romantic relationship. I have been with one woman. I fell madly in love with her in graduate school but she dumped me after a brief situationship and it really did a number on me. I’ve had crushes on women since then but they’ve all been straight. I haven’t had the courage to meet women off of dating apps or anything and since no one I liked in real life has worked out, I’ve basically dated a bunch of men instead - that’s been ok but I can’t shake the feeling that I am either a lesbian or have a strong preference toward women.

I am obviously very familiar with the common story of falling in love with your straight friend and have been good about not doing that (the one woman I dated was bi so I knew from the get go there was a possibility of feelings being reciprocated). Well I’ve finally made the grave mistake of falling for a straight friend (40F) who is a colleague. We work in the same group at my company, and are close to the same seniority level. We became closer friends in the last several months and have been spending a lot of time together. She’s hands down the most beautiful woman I’ve ever seen. I didn’t think I had any chance with her but she told me she’s completely single and made a fair number of jokes about us being girlfriends or having a relationship or us hanging out being “dates” (I wouldn’t go so far as saying she was sending mixed signals but there was a gray area there with some of these comments). I was naive and let myself develop strong feelings for her and I am definitely partially responsible for how close we’ve gotten.

We got dinner tonight and then she came back to my place to keep hanging out. At my place she casually mentioned that she’s 100% straight because we were talking about our mutual friend who is bi. I don’t really hide my sexuality if people ask (I at least say I’m open to both) but people tend to assume I’m straight and I don’t think she knows. Suddenly when she said that I started getting really nauseous. I feel like I have instigated a close friendship - and I do love being her friend - but my true motives were obviously romantic and I feel like such a creep now. Later she also literally teared up because she said no one at our company has been as welcoming to her as I have and how I’m such a good friend to her that she almost wonders why (she has some self esteem issues so has trouble making new friends). At this point I felt truly disgusting and like I had misled her.

So now I feel I can’t let her down and have to remain a good friend to her. I can’t tell her the truth because she will feel misled and also it’s just not an option because we’ll need to interact at work and I can’t let my job get messy (I’m up for promotion soon). I feel insane because I let myself develop these strong feelings in a work setting where it was such a bad idea and one comment from her about being straight brought me down to earth - I know it’s hard to believe but we just hadn’t discussed sexualities before though we both knew we dated men, and it hit me like a ton of bricks how vehemently she said it. I also know I need to work on accepting myself and try to find a healthier dynamic around dating and being true to what I want. But in the near term how the heck do I maintain a professional and personal relationship with her while hiding how I feel? There probably isn’t good advice and I guess I also just needed to vent.