Totally depends on the situation and totally depends on the chick. I have had friends with benefits, that I couldnt have cared less about. There are also the friends, who are just friends and nothing more. If its one of those then I dont really care what they do.
I have also had friends with benefits that I like alot, maybe not enough to be in a committed relationship, but I like screwing them, hanging out and I genuinely like her as a person. I will tend to buy her a drink or two, especially if shes totally into me and I know she thinks of me as someone she wants to be in a relationship with.