Stuck

Hi, I have social anxiety along with just finishing school and recently losing a long term friendship so I really only have one friend (18 like me). I don't talk to people online due to panic attacks if I try to. But it's okay, she's nice and funny but she can be ~selfish~ I guess. She expects me to do everything and pay for everything which I do mostly willingly since I know she does not have much money and I'm fine with that. But it went from the start of the friendship where she politely asked if she could have something to just telling me I have to get something for her. My mom is annoyed too since it's her money because I don't have a job due to physical injury. I went along with this for a few months but then she told me today that I had to get her food and bring it to her house even though she knows that my injury worsened and I can't walk. I know she wasn't joking.

I feel selfish and wrong for complaining about this but I need advice. I can't just break off the friendship for many reasons so I don't know what to do.