Friend just using me?

I have a friend (supposedly best friend) who is 26 and still lives with her parents and doesn't have a job. She accompanied me shopping the other day and my daughter kept saying she was hungry so we stopped in the McDonald's (there's one right there in the Wal-Mart). When we were in line waiting to give our order, my friend never offered up any info as to whether she was hungry or not or going to get anything, so out of common courtesy, I asked her if she was hungry. It's almost as if she was just waiting for me to offer to get her something to eat. Which didn't surprise me at this point because I've footed the bill several times before. The thing that really got to me was that after I had bought her lunch and we ate and left, we were about to leave the store and she was like "Wait. I need to go run and get something." and she comes back with a 6 pk. of beer! So apparently she has money to buy herself beer but she can't pay for her own food? I'm getting a little fed up. Any advice?