<human>: So I have a really close friend, she goes by Z, and last night, her and I were walking to go meet up with some of her friends.  
As some context, we've expressed mutual attraction in the past, and she is/was dating another girl [late 20's F].  Last night we were walking, and she pulls me onto a side road and says something along the lines of 'I'm 100% sure that my girl is cheating on me this weekend, so are you gonna kiss me or what'  
Anyway, I did, and then we met up with her friends and grabbed food. When I had to go, she kissed me goodbye.  We were both sober, so I know it's genuine, but it still feels a bit weird to be in this position.  I've been trying to justify it to myself based off the fact that she's breaking up with her girlfriend, for a variety of reasons, but I still feel pretty weird about it.

Can you succinctly summarize the text in 1-3 sentences?
<bot>: Friend tells me she's sure her girlfriend is cheating on her, kisses me, does it again, hasn't broken up with this other girl yet.  I feel weird about it.  What do I say/do?