That’s a tough situation, green. You’re now in a somewhat-open relationship, and not because you wanted to be but because she forced your hand. That’s not really fair on you. I agree with you that this is not an unconventional friendship, it’s an affair.

If your only hangup with this is the kissing, is it not worth having another talk with her along the lines of: “Look, I didn’t sign up for a relationship like this, but I’m working hard to adapt to it and I want to make this work. Can you not make me a small concession and stop kissing him?”

If it really is her way or the highway and she’s not willing to compromise at all, she’s being pretty selfish. Still, it sounds like you’ve got a lot together and you’re both in flux at this time. So I would say, try to make it work. Try to accept this new situation as it is and continue to love her. You may reach a point where you know for sure you won’t be able to, but until then it’s worth your best effort.