Helpfully, the Times today had a very short paragraph about this, the main points of which I will list. They called it GCSE/A-level deflation and suggested ways to address it.
1. Exams are a rite of passage and the culmination of the time spent preparing for them. Many students feel it's not worth it as the 'finishing line' has disappeared. However, not to finish with your cohort carries its problems too (my observation).
2. Validate their feelings and recognise it's hard at that age to maintain motivation. Ofen helping them with a plan and breaking the work up into small chunks helps. They can see an 'end'. Emphasis that grades achieved are still grades even if not delivered in the exam hall.
3. Try to focus on the fact that what is certain is that they will leave with grades and working for better grades is a good idea.
You are probably not able to be with your GD at this time but you could encourage via online conversations - e.g. you tackle that essay and I'll clear out that cupboard I meant to last lockdown. After 45 minutes we'll compare progress.
I'm a retired teacher, and my betting is that many of her friends are doing more than they say. They just want to follow the crowd.
If you know the subjects and exam boards you can look up online how they award the marks for each grade, what they expect in a piece of work. That can be a real motivator. They often haven't a clue, no matter how often you tell them in class. Be careful though, you do have to know Board, Syllabus number, units entered etc. For the Art and DT knowing what they expect would be useful.
If the school is doing what it should the work set by the exam teachers should reflect this. Many students were caught out last year but motivated schools set extra work to help them with grades.
Good luck with it. A hard task but worth the reward. And, as many have said, not the end of the road if grades do not reflect her true ability.