Mom called me selfish

So I get up at 5 am every morning to get ready for school. My bus comes at random times so I never know when she's gonna pull up. So a little while ago at 6:09 my mom came to me and told me to take my grandma's blood sugar. I told her I was on a time crunch and she got so mad. She called me an idiot for saying that and selfish. Selfish because if it's not for me or about me I don't wanna do it. I am 17. I will be 18 in two weeks. She calls people names when 1) she doesn't wanna do it and you can't and 2) when she doesnt get her way. Whenever I do something that she knows how to do wrong, she yells at me and says I don't wanna do it and calls me a name. She does my grandmas routine with ease and gets mad that I can't or don't know how to. I know for a fact if I miss my bus she isn't gonna bring me to school. I find this whole thing stupid. Was I wrong?