I had horrendous skin as a teenager and it made me feel miserable. I was also referred to dermatologist who prescribed roaccutane and a steroidal skin treatment and it literally did nothing for me at all.. my skin might have even got worse!
I hated the roaccutane. I had to have regular blood tests to check my kidneys could cope and that I wasn't pregnant!!! It's also not a long term option either so if it's not working it feels even worse..!
Ultimately, only two things worked for me: short term: antibiotics. Long term: the pill.
I would occasionally come off it to test whether the acne would come back.. it did until I was probably around 26/27ish I'm afraid to say.
What I would say however is that, as tempting as it is for your daughter to try to hide the acne, a lot of these treatments will damage her skin in the long run and when her skin clears up she'll be left with issues as a result. My skin is 'crepey' in places, enlarged pores and wrinkles that I'm sure I shouldn't have quite yet!!!
I fully appreciate how painful it is (both physically and emotionally) to suffer from the acne but she may also find that the make up actually highlights the acne rather than conceals it (even those designed for acne skin) and she'd be better off without.. but without seeing her I couldn't say for certain. That was just my experience! I know it acts like a mask though and if it makes it more bearable then fair enough!
Also, hair shouldn't be used to cover the face as the natural oil in the hair can be too heavy for the face skin.
I also used sugar as a gentle face scrub and Clinique do a body scrub with menthol in it (can't quite remember the name but it's in a fairly large tub) which I also used.. I found that really helped. You'll be told that exfoliating too often is too harsh but I found it helped my skin to regenerate and genuinely felt it helped.
Something my mother now says to me that is she really felt for me but she also saw how my personality bloomed because I couldn't even try to rely on my looks... it really is a trial - and a cruel one for a teenager - but she will come through it and she will be stronger when she does. I know that doesn't help now but just remind her that it's not forever... and that this isn't a reflection on HER or her personal hygiene or whatever.. it's just an unfortunate (probably hormonal) imbalance which she'll get figured out soon!
If it helps, my skin is now really clear and has been for about ten/twelve years. It is very rare I even get a pimple let alone a 'proper' spot. I haven't had a big red angry boil like spot in what feels like forever!
(As an aside: more recently, I have become a vegetarian and for lunch every day I eat a plate full of raw veggies and salad - the more variety the better- and I've really noticed a further improvement in my skin. Could be worth a try?!)
Sorry.. didn't mean this to be so long!!!!
TL;DR- I feel her pain from 1st hand experience. It sucks. Try antibiotics to get it under control, then the pill if she hasn't already. Eat more veggies. Remind her it's not forever and this doesn't define her. X