Girlfriend Is Needy or is it just me?

I think I may have an issue with my gf. She is acting like an immature child and I tell her to toughen up. I encourage her to be strong and use her intellect to solve her problems rather than whining about it and demanding sympathy from her bf. I do sympathize with her, but she is pushing me to be her little slave that does what she wants. Just yesterday, I start kissing her neck very sensually and she demands I stop and pushes me away. She gets all offensive when I want something from her such as despite the great lengths I go through for her daily and despite that fact that we never get it on. I do my best to be the best boyfriend I can, but it's just never enough for her. I've basically come to the conclusion of "**** this" after realizing she's not worth it in the least bit.