Who is wrong here?

Whats up bros. I have never really been to the lounge, but have a weird question. Broke up with my last girl 8 months ago after 4 year relationship. We realized we aren't compatible, and now she is like my sister. Well, I have been hanging out with one of her best friends, and things started to happened. I am now the official talk of the town, mabey even the state! lol She moved about 20 minutes away, and has had a boyfriend sdince a WEEK after we broke up. I don't care, as I don't like her like that anymore, and thought the same about her. She rarely sees either of us anymore, only on the phone do we talk. Is it that wrong to hook up with her friend? I think we might really have something, she is really cool and JUST like me. I promised I wouldn't let things change between me an my ex, but she is pissed! WTF am I supposed to do? I do what I can to make sure she is happy, and now she seems to be selfish to me. What is the opinion on this? Am I an asshole, or Should I just proceed and take it slow?
I need some opinions please!

Fuck her, do what you want...you are no longer a couple...

Generally the rule of thumb is you don't fuck around with your buddies ex's. But since this isn't the case for you, then yes...fuck her and do what you want.

Well........... She also happens to be one of my friends ex girlfriends. they broke up two months ago, and he isn't a close friend. This sucks! Why do I get myself into these things?

dude all is afair in love n war!

fuck that bro do what ever makes you happy. your ex should understand that you have to move on it's been 8 months. even if it is one of her friends you said that your ex is like a sister to you right. then she should be a friend, and be happy for you that found someone not selfish like she is being now..

Golden rule never date an ex,s friend

Why ............try it and find out the hard way lol

Hmmm. mixed opinions on this one. I am going to her place now, And I think I am going to go with the majority! lol