One of my best friends girlfriends likes me and I feel the same way

One of my good friends met a girl who he started dating about a year ago and we all became good friends pretty quickly. We would all hangout pretty often, and I always thought she was pretty but would never ever think of her in anything more than a friend. Well, a few months ago I had lost somebody very close to me and she was one of the only people who constantly reached out to me and helped me grieve (she has been through something similar in her life). Ever since then we’ve become super close and honestly she’s become my best friend. She recently started telling me how she hasn’t been happy in their relationship for a long time, and told me that I was the only person that she feels like listens to her and truly understands her. We found out that we have an inane about of things in common and have been through a lot of the same things. I started to have feelings for her as well but wouldn’t ever think to act on them at that time. Anyway, I tried to talk to other girls from dating apps to get me to stop thinking about her. But nobody compares to her in my eyes. But she recently told me that she wanted me, and I told her I wanted her back. I truly dont know what to do and I’ve never been more lost in my life. I feel like a piece of shit for even thinking these things but I can’t help it. If anybody has been in a similar position please help me. Is this something that could ever work out? If they break up if there any chance that we could be together? Is it something that would have to be kept silent and be hidden from everyone? Am I just a terrible friend who ruined his friends relationship? It really feels like this girl is my soulmate and I really do think that we were meant for eachother but idk if we’ll ever be able to move forward with it. I’m so lost and confused and angry with myself all the time about this.