All the signs I read about on the internet are there:
sudden lack of motivation for any hobbies/interests; poor personal appearance, hanging out with a new bunch of friends to the exclusion of her other long-term good ones etc...
She is 16, totally defensive about any attempt to open conversation and if she doesn't like an instruction not to go out or to be home at a certain time, she just ignores it. She is turning into a completely different person before my eyes!
Any advice?