Yes, I get that she's just finished her GCSEs, I get that being 16 is tough and it's a way of exerting control, but I honestly don't know what to do.
If sitting in her room looking at her phone made her happy, I'd be all well, crack on then, but it doesn't. Today, she's refused to put suncream on (I know I shouldn't nag, but my friend died of skin cancer aged 20 and it's a non- negotiable for me), screamed at DH about leaving some stuff out in the kitchen, listed a load of things she's not doing (prom, holiday, going out, weekends away, getting a job, voluntary work) and has gone to sit in the dark in her bedroom, having broken a plate by slamming it down.
This isn't an unheard of mood state for her tbh, and it really worried me that without the structure of school, she's just going to spiral down.