It's all about how well the differences work together.

Well, I guess that she thinks that ours don't work well together. Her excuses weren't a cop-out. She's not cheating or anything, she just feels strongly that in order for us to work together, it would require that both of us change too much. She's all about being her own person, and hanging on to who she is. Even if that means not growing into a better person, and living in the past. (of course that last part is my opinion)