To be angry or not to be angry...

[his_x]

So, I'm going to keep it real. And I hope nobody gets offended. I can't decide whether I should be mad at someone or not. I should be b/c she kissed my boyfriend multiple times days after we broke up. And it's not like she didn't know. But, he did actively persue her. However, she isn't with him, maybe b/c he didn't want her, and she is now with his brother, who I really dislike.(But only for the sheer fact he hates me for some unknown reason)At the same time, I think she really is a super nice girl and we could probably get along well. I just really hate girls who do that. Who take advantage of a vulnerable situation for their own gain. I would never hurt another person like that. And for her to recently come out of a breakup, she should have understood how I felt.

Does anyone have an opinion on this?

P.S. Girl in question, if you read this, I hope you will understand my position.