What are the positive aspects? Does the positive outweigh the negative? I would make a list of the good and the bad and ask yourself "What is my best choice here? Put up with it or tell her how I feel?"
I would simply tell her: I cannot continue paying for your meals when we go out, and I could use some help with gas expense when I provide your transportation. If she is really a friend she should understand and accept this. Sometimes close friends do not realize when they are taking advantage of us -- especially if we are not open and honest with them.
