Hey Sushee,
This all sounds so familiar...
I was Dux of primary school, top of the class with another girl in Yr7 etc etc and always right 'up there', and it was always assumed that I would go on and go to uni, do something that a regular smart kid would do and get a really successful job etc etc etc..
But I had no idea what I wanted to do! I can't imagine how many people would at that age, considering they start 'career planning' of some sort from the start of highschool - 12 or 13yrs old (!!!)...
There was little being taught in my school that I felt was worth learning, and I decided to 'drop' a whole lot of classes during yr10 (usually planned sleep-ins or leaving early or hanging out in the photo lab instead )
About half way through yr10 I decided I had to do something about it if I were to continue on to yr11 & 12, so I applied for an academically selective school in Sydney (a lot of it was to do with getting out of a small country town!.. but still with a view to education) and was accepted.
I started Yr11 in the city and lasted about 2 weeks. Some of it was culture shock, and a lot of it was realisation that I was going nowhere.
I was studying something along the lines of: Music, Drama, Photography, Computer Studies + the compulsory Maths & English; and it became apparent that apart from an Arts degree, I wouldn't get to Uni anyway!
So I left, and made a way for myself, paying my own way, living out of home from the age of 16, working full time and getting myself acquainted with the real world.
I felt that by the time all of my friends back home had finished their HSC's and moved to the big smoke too, I was way too far ahead of them. I was so glad I had been working those 2yrs instead, as they'd just treated their HSC years as any other year, not applied themselves and had no desire to, and were simply just there with little other reason than to please their parents. Most scored poor (or negligable!) UAI's and constantly mention how they 'lost 2yrs of their lives'.
I've had 5 years out in the real world now - I'm currently working in a retail management role and in the next couple of years will either be studying my HSC or an adult Tertiary admission test to get into Uni - NOT because I can't get a good job otherwise, but because I have finally found something I want to learn and am finally of the right mindset to commit to study. I can't imagine preparing to do what I want to do at the age of 15, and I don't think I would have lasted had I done so.
I feel like I have so much more time to plan things the way I want them to be, and I don't resent leaving so early at all.
It has worked perfectly for me, and I think it is a very real option these days.
I wanted to tell you this about myself to show that it can work, and maybe to understand some of the motivations behind this. School isn't for everyone, and as much as 'I hate school' might seem like a teenage cliche, some kids do have a point.
I'm in no way trying to tell you you're wrong, but just show a different viewpoint. If she's a clever girl then the likelihood is she could be on to something.

Good luck with it all, feel free to email me if you want to talk about it.

Just remember that she is still your clever little girl, still full of promise. Choosing not to follow mainstream education shouldn't take that away.

Kate