How should I react to being strung along?

So this girl has been stringing me along for a couple months. As soon as I started to figure it out I backed off completely. I get an attitude every time she asks me to do something for her when she is completely capable of doing these things for herself. For example, she asked me to go to the store to get paper towels even though she was going out and I had only one errand to do. Am I wrong for having an attitude with her even though I feel like I have been used to just do things for her and pay for things for her? With that being said I am already planning a move very far away from her. My ultimate question is should I just say no and try to be nice or am I justified in having an attitude? I try not to make someone feel bad but when I've been treated like shit and feel pretty bad for falling for her games I get an attitude because of it.
How should I react to being strung along?
How should I react to being strung along?
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