AIO for wanting my sister to pay me back?

It's not a whole lot of money in all honesty but for a teen who only has a summer job it is. I gave my sister 30$ this morning after she offered to get me anything from TacoBell, I gave her more then I thought she would need for the food because she said she was going to the mall after or whatever. It's kinda always been just curtesy to pay someone back after they lend you money right? In my family we've always payed each other back but I don't wanna blow this out of proportion. After a few hours she came back with the food, when I asked for the money she said she used it to pay for her and my food. I was kinda shocked because idk I thought she would atleast have something to give back to me? She's already borrowed money from me in the past and hasn't payed me back for it but I let it slide becauses she's my big sis and her job doesn't really pay her well. AIO for wanting money back?