Why?

One things I have always wondered is why people think the world revolves around them. One of my friends missed a class that we share together yesterday because she's sick. She asked me to talk to the teacher, and I said I would. She kept texting me about it when she knew that I would be working on homework for that class. I tried doing homework and responding to her texts, but I had to work really hard on trying to do my homework. Then when I was in class today, she texted me again asking if I could talk to her later TODAY about what we did in the class yesterday. I told her no. If she needs to know about class that she needed to talk to the professor. Then she wrote back saying you don't even have 10 minutes to talk? I said no. Then she wrote saying she would have to figure it out on her own because the professor doesn't have office hours. I know she did it because she knows what a pushover I can be. I told her that I don't have time today, but I might be able to talk to her tomorrow. I know I probably do have time to talk to her about it later, but she shouldn't assume that I can be at her beck and call. I'm not her bitch to order around. One text is all it takes to answer a question. I know your defence is that she's sick. So what? I cried IN CLASS because I was so stressed out. I still made it there and did my homework. Did I happen to mention that I was also sick at the time? Not to mention that I hadn't eaten like at all yesterday either. Oh yeah, I also forgot to mention that I was running on maybe 4.5 hours of sleep. Whatever.

I know I write about myself in this, but this is supposed to be about me. Any advice on how to handle this with her?

BEDA days missed: 4
BEDA days caught up: 1