I used to do this. What happens is you find out people are only nice to you because they can use you. If you cease to be useful to them, you find out what they really think about you. Women in particular only deal with men they arent involved with, for what utility you can provide them. Once you stop, they despise you because they cant get anything they want from you. Now I take care of friends and family that value me and actually care about me, my time is valuable and the one thing I can’t ever get back, so if I spend it on people, its people that are important to me.
You’re right that true friendships are reciprocal in nature. If she’s not willing to reciprocate, then it eventually becomes impossible.
I read a really good analogy to this. It is called ‘the coffee cup’.
When you help somebody, you empty your coffee cup a bit. When they return the favour, they fill your coffee cup a bit. If they are draining your cup and never filling, your coffee cup will eventually become dry. So, you have to keep track of the cup to see what is going on.