@NadiSel I'm sorry your DD is in this position. It must be a horrible blow, especially after what I can imagine was a very stressful year last year.
Could she speak to the school to see if there is anything they can do for her re Chemistry? Although there isn't space for her in class, could they set work for her so that they can mark it and have something to base a grade on?
If that's not possible, are there any external exam centres that could help? I've seen these mentioned on other forums and I think they were able to provide CAGS last year.
Also, we still don't know what the alternative to A levels will be. There may still be externally set, externally marked assessments of some sort - I think this is what Wales are doing, so there may still be a way for your DD to sit these and get her grade.
Has DD applied this year or does she hold a place from last year? It could be worth contacting the Unis and asking them what their take on it would be. Assuming she can get her grade up to an A in Maths, and has an A in one other subject, she will have AAB, without sitting Chemistry, which could be acceptable if she has an EPQ or if the Unis are being flexible to the situation.
I did see someone reference a facebook group called Tutors and Exams and I just had a look. It seems to be a private candidate exam centre. You might find some good, helpful info there from people in a similar situation.
Good luck - I hope things become clearer soon.