OP, I hope that when you're "hanging out", you mean you're sleeping with her.
You obviously have feelings for her that she doesn't have for you. I don't care how much you agreed to only be friends, you want her. Meanwhile she's having you take her home after phucking someone in another state.
You, sir, are a sucker. But, it's the power of the vag....we've all been victims to it!
If she is your friend, treat her like one. I don't think you should stop hanging out with her. She is your friend, after all. But I do believe you should stop going above and beyond. The next time she asks you to do something you should ask yourself, "if this were someone else asking me, what would my answer be?"
Spending on gas is like paying for a ticket to ride a rollercoaster - Crazy Bimmer