I (26M) started a FWB situation with my neighbor (35F). I’ve realized I’m not sexually attracted to her and need to end it without losing the friendship. Help?

I’ve been hanging out with my across-the-hall neighbor for about a month. We have a great friendship, as far as I can tell. We play chess, video games, and have some good conversations. There was some sexual/romantic tension, so a week ago I suggested we try a "friends with benefits" dynamic since she’s moving out of the country soon anyway. She agreed, and we’ve had sex several times since.

However, now that the "mystery" is gone, I’ve realized I’m just not sexually attracted to her. There are some physical/hygiene dealbreakers for me that I didn't notice before.

Last night, we got high together, and she tried to initiate sexy time, and I ended up having a bit of an anxiety freak-out and asked her to leave. Now things are pretty awkward.

I really value her as a friend and want to go back to how things were before we hooked up, but I don't know how to tell her I'm not into it anymore without being hurtful or making living across the hall a nightmare.

How do I tell her I want to stop the sexual part but keep the friendship?

Do I tell her why I’m not attracted to her if she asks?

How do I handle the potential fallout since we live in the same building?

TL;DR: Started a FWB thing with my neighbor/friend. Realized the sexual chemistry isn't there for me. Had a minor panic attack last night when she tried to initiate. Need to end the benefits while keeping the friend.