<human>: Can you condense the text into a few key points?

Long story short, my roommate asked me if there was anything needed for the apartment so I asked her to get mayo and bleach. Later she comes up and asks if I can pay her back because "she doesn't use those items". Now before you think its four dollars just give her the money. I have spent A LOT more than 4 dollars on items for the apartment that I never use. I know this isn't tit for tat but it is very frustrating when my two other roommates and I buy things needed for the apartment and she gets mad about 4 dollars. Also, why offer to get things for the apartment and then ask for the money. She has done this before, asked us for items and then complained how she doesn't use them. It is petty I know but my roommates and I are tired of hearing "I don't use it" when we all purchase things necessary regardless if we use it or not. This is just one thing she is very selfish about. So this is just the tipping point I guess. So how have you handled dealing with a selfish roommate? Also I try communicating with her and it just goes in one ear and out the other.
<bot>: Roommate is selfish and petty, won't buy anything for the apartment unless she uses it when everyone else does, how do you deal with a selfish roommate?