PF

I have two friends that are 19 and 20 - I'm 26. One has asked me to buy her alcohol before and I felt uncomfortable with it and politely declined, apologizing profusely. She was rude and obviously upset with my decision. I told her I wasn't comfortable with it, and she said that if she was 21 and one of her friends asked, she wouldn't even hesitate. First, I lived 20 minutes from her and wasn't even going to be at that party where obviously no one else was of age. Somehow, we moved beyond that and became a little closer. But now I'm being asked again. It's not convenient to drive across town for the sole purpose of transporting alcohol. Especially with gas prices the way they are. It's not so much that I don't trust her, as much as it sucks to be the "go to" person every now and then. I'm in my PJ's, I'm cleaning my house - do I want to drive 20 minutes across town after going to the liquor store? NO. I feel bad, but I said no. And so far, I haven't had a text back. Any advice?