My friend is starting to annoy me so badly now and I don't know what to do?

We've been friends for a good 5 years, but she's been starting to really annoy me lately. She's so whiny about everything and seems to only want to talk about herself. Whenever we're talking about something and she wants to change the subject, she just cuts me off. And then there's this teacher at school she really hates... she tries to be "all that" and show him that he's "not so great," but to me it's just making her look stupid. She raises her chin when she corrects him, and just looks down her pudgy cheeks with her face in the air... ugh. She tries to sound smart but it's just annoying and nobody cares. And she also complains about everything, including test scores when everyone she's whining to did worse than her-- how insensitive is that? And she always tries to make herself look better than everyone else. If someone asks a question to another classmate and she's within earshot, she just answers it even though it wasn't directed to her. She thinks it's funny to embarrass me by saying boys' names when they're within earshot, like "Oh, did you ask ___ out yet?" really loudly. I've told her to stop multiple times, but she just giggles and ignores me. And then there is an annoying grunting noise she makes under her breath a lot... even during tests she does it. I wish she'd just grow up...