How can I get along better with my mom?

I'm 15 years old, and I've been fighting with her over almost everything since I was 10. I know I'm not blameless, I talk back to her, but only when she gets mad or yells, and I understand that's not an excuse. She's not a bad mom or a helicopter mom, she doesn't care what music I listen to, and lets me watch the t.v I want to watch, and lets me wear what I want, as long as I don't dress inappropriately. But she's ALWAYS angry. I know alot of it is because there are 4 kids in the family, and she gets very stressed out. But sometimes she goes way over the top and that isn't a reasonable excuse. Our opinions are polar opposites. And whenever I ask her for help or advice on my friends, she acts extremely condescending and just insults my friends and their actions. And she talks about my friends to her friends, saying to them when I am there "I'll tell you exactly what I don't like about this one later." I want to be able to talk to her about things, and ask for advice, but I just don't even feel like she's my mom, just a boss. I'm scared that we have almost no relationship, and how we'll turn out as I get older. I can't talk to her because she gets furious if I don't agree with her, even if I just ask her about friends and stuff. How can I fix things??