There have been a lot of great posts on cheating: what it is and what it isn't. That being the case, I'm not going to bother throwing in my two cents -- at this point it would likely cause an avalanche of pennies.

I'm chiming in simply to say to the original poster, prehaps approach this topic with your partner without making it an issue of cheating and infidelity. As this thread clearly shows, cheating can mean different things to different people. If you and your partner get caught up in definitions and semantics, she's going to continue to focus on the fact that in her mind she didn't cheat and therefore there isn't a problem. Communicate to her that you understand she doesn't believe she cheated, but you still feel as if your feelings were compromised and that you're hurt.

Rules and definitions are fine, but relationships aren't courts -- getting out of something based on a semantic loophole isn't really winning your case when what you're trying to accomplish is building and maintaining a partnership. It's possible to be "right" and justified and win the argument, but if you cause damage to the person you're supposed to care for in the process, what have you really won? Perhaps this should be the conversation you and your partner are having.