Ask the college. It could be that they won't accept her onto a Level 3 course but will accept her onto a Level 2 course (if they run one in the subject she wants to do). If not, it might be worth trying a different college.
If there are mental health issues affecting her studies now and that's why you are concerned that she won't achieve the grades needed, then it would be a good idea to get those issues documented soon (before she sits the exams and gets the results)
It's great that Maths and English are the ones you are confident about.