is there something wrong with me?

Somethign i should add. Just because you're a nice guy doesn't mean you should let people walk on you. Also being a nice I can say this from the heart, there are people in your life that want to stay in your life because you are a nice guy. They dont offer anything in return for your friendship but instead take alot of out of you; they can run you around until your blue in the face!

Something all nice guys have to learn is when to stop being nice to people that dont deserve it. You might try not taking her calls and deleting any messages she leaves on your phone if you truly aren't strong enough to tell her off. Whatever you do dont let her harden you, if you stop being nice to other people on account of her, shes won!