Admitted Feelings For My Best Friend

Me and my best friend were extremely close for 3 years and it was the closest relationship either of us has had with another person. Last year, we were both fresh out of abusive relationships and were wary of new ones so we stayed single for months. I'm guessing that led to us flirting since we had nowhere to direct our feelings. For example, she'd randomly send nudes and say we should date but we'd laugh about it. I think I had platonic goggles on because I didn't see it as anything else other than jokes. Anyways, we had a deep conversation about relationships and our past abuse and we did the usual "you deserve the world you're so great" talk and it ended up with how we would be as a couple and how great it would be. Looking back, I realized she was trying to get me to actually do it and not as a hypothetical. But after that night, I started seriously considering it and decided it really would be the perfect relationship. We already hung out almost everyday and did everything together. But the mistake came with me being too scared to ruin our friendship so I didn't do anything about it for a while. Then fate intervened and the same night I was gonna tell her, she met a guy and I was hoping it would be a fling but they've been going steady for a while now. I asked her about that period where we flirted and discussed hypotheticals and she admitted she was trying to start dating me but that I gave off the impression that I wasn't interested. That news secretly crushed me because I felt stupid for throwing the chance away. I tried dating to get past it and have had good luck in it but I can't help but compare them to her so I end it. Me and her had an instant connection that I can't find in anyone else. I ended up telling her two months ago that I felt the same way for her that she did for me but that I wasn't trying to homewreck her relationship or anything. She said she understood my perspective and that it's valid because she did a lot trying to get me to say something last year. She even agreed to stay friends because of the fact that I respected her relationship she wouldn't act on my feelings. She hasn't replied to me or seen me ever since then. Even during her relationship we were still hanging out all the time and taking trips together but that all stopped. I know it's not healthy to do "what ifs" but knowing how both of us are, I keep thinking about what we should've been. I have so much self hate for myself and I'm just constantly angry because if I was just even one day early instead of being such an evasive overthinker, I would be in probably the healthiest and happiest relationship I've had. Even if we take that out of the equation, I feel like I really don't matter to anybody because given all of our history, she doesn't seem sad about losing me. If the person who knows me best doesn't miss me, who will? The whole situation put me in an existential crisis.