When I was a child I wanted to pick up dog poo. Then I wanted to be a translator in Paris after watching Moulin Rouge despite not speaking a lick of French. After that I wanted to be a barrister despite having the attention span of a gnat.
Kids want to 'be' things that they understand. A nurse infers she wanted to help people/work in healthcare or have a very ordinary job and she will.
It's so engrained in our society that kids follow a traditional route. Get excellent GCSE's, go to college for sensible A Levels, go to university for a career and then get a job for the rest of their lives. That's not the real world.
She's seventeen, she has her ENTIRE LIFE to figure out what she wants to do. Right now, honestly? She's seventeen. She's clearly not academic so as long as she doesn't fail it's OK, even if she does it's OK.
Is she a good person? Is she capable of looking after herself? Can she hold down a part time job? Can she be responsible when she needs to be? At this age if that's all she can do that's fine.
I had undiagnosed ADHD throughout school and the pressure made me feel suicidal at times, I just wanted out of education. My Mum became ill during college and I honestly used it as an excuse to barely pass. I finished college and went straight to work and survived on a little over minimum wage, absolutely balling and living my best life as my friends went to uni.
By my early twenties I had a more realistic head on and decided to focus on the future, I went back and retrained and now have a thriving career. I was a few years behind my friends but who cares? I did it my way - she must do it hers.
I find it unfair of you to state you will have to focus on your other children's education and not hers. Would this have been your attitude if she had gone to uni? Education does not always have to happen in a classroom, there is a massive world out there and if she decides to never get another qualification in her life that's OK.
She sounds driven in her part time job, she may open her own business, she may find her calling, she may decide to get a job in admin and work up or start an online platform, maybe do an apprenticeship. Who knows? She's little more than a child, seventeen is too young to expect them to know what they want to do for the rest of her life.
She knows she doesn't want to follow traditional education. Brilliant. One thing off the list, if you remove the pressure you may find she becomes more open to suggestions.