I had a job from Year 9 to Year 12 and I think it was a positive thing - you can always plan in advance to take some time off around exams or due dates if you need to, but I think it was useful for time managment and also to be in a work environment before you leave school.

However, I'm not sure how you're going to make her get a job if she doesn't want one - just withold the money?, because won't she just sabotage the interview process?

GL!
Good luck!