Yes. My live-in girlfriend of ten years suddenly developed feelings for another guy during a manic episode. She assured me she never cheated, and we're still friendly, but she won't do anything affectionate with me now (unless it's something small and I initiate it).

I've never snooped her phone, but I did notice that she changed the code to unlock it recently, so I'm pretty sure she is and was talking to him on a daily basis after I asked her to stop.

It's tough right now looking past the stuff that's happened, but I love her and I want to help her get better, because I don't really think she's at fault for actions she wouldn't otherwise take if it weren't for the manic episode/s. I just want to focus on letting her start treatment and supporting her the same way I did before all this started.