Am I in the wrong?

I have a friend who watched my child overnight last night, I watched her daughter overnight the night before. Today when I went to get him she told me I should buy her lunch I didn't charge her to keep her child and even took her home myself. I had bought her and her daughter lunch twice earlier in the week. Am I in the wrong for not buying her lunch? I thought it was pretty fair since I watched her daughter and bought her lunch a couple days before and shouldn't have to buy her lunch?