Ok, so, I've read through all the comments and I think there is one thing we're all forgetting. Amy is socially inexperienced! She's never had a boyfriend before, she's never broken up with someone before. While I do still believe it's cliché that she turned to another man after being heart broken, I think that's what she did it! The only examples of romance she's ever seen were in movies/tv shows, and in her friends' relationships. Now, it seems to me that she's asked herself "What will help me ease my pain?" and tried all the ways she only knows how. She turned to another man, because she thought it would make it easier for her. I hate the fact that another guy kissed her, and I bet she does too.
That is, if this guy is even a date. If Stephen is going to be a recurring character (oh my god I hope so!!!) I really really think he will be family.