FWB never lasts forever. Either it fizzles out or you both catch feelings and enter into an LTR.
In this case you caught feelings she didn’t so it fizzled out.
No big deal bro, go get a different FWB.
I would say that I did not catch feelings, but feel she was starting to, and kept convincing herself not to.
Example, one time she said that me not much of a reader, "this is why we wouldn't work out"
Another example she said after sex "We could never date, we have nothing in common but we have sex in common"
She said over and over "I don't want to do drinks or meet your friends" and I said "Yeah I'm fine with that"
She would also say "Don't catch feelings" and I was like "Yeah, I know"
So yes, I knew it was all out there.
She'd start sharing songs with me about love, or broken hearts, etc -- so I kind of wondered if she wanted me to make a move or progress this -- because an FWB at the heart of it is about casualness and hooking up -- if you look back to my original text I said "I thought this was kosher and casual" and then she said "Until it wasn't" -- meaning SOMETHING changed at that point (but doesn't have the audacity to tell me)
I think what happened here is she's saying "I like you but I need to see my other options" -- and I'm fine with that. At the very least, I know that I made her feel good about herself (never any arguments, or drama)