I did something similar when I was 16 and I have regretted it ever since.
I went to do a floristry course. It was hard, cold and dirty. Hairdressing isn?t much more glam. Sweeping hair, washing hair (especially in cold winters - hands wrinkled), the chemicals and any reactions you may have from constant exposure etc. The nits and lice, which are more common than you might think. Most of those who train don?t stick it and nearly all end up supermarket check out assistants. Most of my course mates ended up there.
The problem is that it is unbelievably difficult to get out and change afterwards. I know posters keep suggesting she can change her mind, but in reality it isn?t easy to make that change. She will have left school and can?t go back. Her options will be A level in an FE if she is lucky or night class.
I did my A levels by night class and was stuck working in floristry for nearly 10 years until I married and had a family. My A level grades were hampered by the teaching and classes I was in. This in turn affected my choice of university and course. My husband supported me through college because I couldn?t get any support elsewhere as an adult returner. I got a degree and went on to be a teacher but I regret the loss of those years now. Had my parents kicked my ass severely I would thank them for it. The problem is they were all about letting me make the choices and at 16 you don?t know what it is all about. I was an arrogant toad who thought I knew it all.
All I actually wanted was to be free of the school I was in and to not have to take any more exams for a year. In fact I wanted to stop at home and do nothing for that year. I wanted a boyfriend and I wanted to go out and do shopping and things but there isn?t a lot you can do at 16 but at 16 you don?t know that (don?t know what things I did want to do really with hindsight. I was just mad about a lifestyle I saw on TV and such) Just have time to slouch out and wait to be found and whisked off to some fantastic life. That isn?t realistic but most 16 year olds don?t know that. Doing a floristry course was the next thing (the beauty course was full otherwise I would have done that). I just wanted to be a girl and not be pressured to do more and more exams. A beauty queen, a singer, a model, they were all in my head.
I think the OP needs to kick her daughters ass and tell her she gets one bite at the cherry after which the way back is hard and the doors do not open in the same way again. Get her to take her A levels at least - and in school, not an FE. Then she has options.