Eh, I think it's the teenage thing. Unless she was like that when you were younger...
Parents tend to become more stressed when they have teens in the house, so they're more apt to be hypocritical and "near the edge" per se. Seems stupid to some of you, yeah, but it does sort of make sense. I know if I had a teenager running around I'd pull my hair out in fear of the brat getting knocked up or knocking someone up since a lot of teens tend to be so horny that they need castration.
My mum starts shouting at me but then when I win the argument with loads of sarcasm she gets annoyed and slams the door. I laugh. She shouts at me to stop shouting. Oh, and if I say something in the friendliest voice I can manage I have an attitude. So all parents are hypocrites.
I think all parents are hypocrites like that. My mom does the same thing. She can throw a fit and scream, and it's all in fun. But if I raise my voice just a tad, then I'm automatically a bitch who's in a bad mood. She thinks she knows me, and yet she somehow still doesn't realize I get easily annoyed in the first hour or so of waking up.
But I'm moving in a few months, so I'll deal with it.