We are not there yet...one more round of chemo to go, so I am also keen to hear others' feedback on this. However, have your DN's parents spoken to their consultant about rehabilitation options after the end of chemo, and whether this might help? It's something I had to push hard for, but we've finally been referred to The Children's Trust in Surrey (just waiting to hear back whether we've been accepted). Apparently they offer residential rehab at their centre, which includes physio, occupational therapy, pyschology support, school, hydrotherapy etc., all onsite. It might not be right for your DN, but possibly worth asking about.
Does your DN have a wheelchair she can use to help manage energy levels? Have the school done a risk assessment? Is there a community physiotherapist and occupational therapist you can ask for further support from in terms of suggestions for gradually building up her strength?
My DS's school weren't particularly supportive, and I had to suggest everything I felt was a reasonable adjustment, including how frequent and how long DS's school days would be. (He's only been a few days in the last 8 months, but at least we now have an agreed process with the school which, in and of itself, is a small mircale that took months.)
I suggested 2 hours a day, for two days a week, which could increase as and when DS felt able to. I also asked if they would consider practical things like, as there's no elevator in his school, to arrange classes that were on the same floor to be back-to-back, where possible, to limit the amount of times he has to walk up and downstairs.
So glad for your DN that the scans are showing no remaining tumour. I hope all improves from now on.