How is it "her" loan when she took it out to pay for YOUR college tuition?

Also, are you patting yourself on the back for "occasionally" putting gas in the tank of the car you drive? Does that mean she pays for everything about the car and all you do is put gas in it sometimes? You "share"/drive the car, but she has to pay for the insurance, gas as well, repairs, maintenance, and any parking fees at your apartment or wherever you keep the car?

Also, you pay for some of the food you eat, but you think she needs to pay for whatever else you eat but don't pay for? Maybe you should use some of your savings and fun money to give her that $60 for groceries. An extra $2 per day doesn't seem a lot to ask for especially if you eat food that's in the house. But if you don't want to pay that extra $2/day, then maybe you need to get for your room a mini-fridge and a portable burner and eat only what you buy.

It's nice that your mother is letting you live there without you paying rent. I'm thinking she gave you your own bedroom and you aren't sleeping on the living room couch?

Because if she moved like you tell her to and she gets a 1-bedroom or a studio, are you going to complain about not having your own bedroom and/or having to sleep on the floor?

AITA for refusing to help my mom pay her bills?

YTA, because it sounds like you think she has to pay for your food too. You made yourself sound really entitled, self-centered, and selfish.