Nice response Ginger and this helps the support of the notion of see someone who actually has an interest in the biomechanics of the entire gymnastic repertoire. I can imagine this involves a lot of tumbling? Perhaps also a lot of landing from mini trampolines etc. In more advanced landing from uneven bars.
I once heard it said that unless a young female gymnast had at least 2 levels of spondylolithesis (essentially fractured vertebrae) then they could never be any good! campbells7, this means excessive curve in the very low back so they can create a very (hyper) extended line in arabesque etc. Hyper movement at L4/5 and L5/S1 could mean that the higher levels are less mobile but that would need to be proven. One could assume that those levels could also be irritated by excessive movement.
All of the above factors place the pelvis and therefore the femoral heads in less optimal positions (that will load the knees excessively). I think everyone could go on and on about the possibilities suffice to say that the patella is exhibiting signs of overload. Nothing abnormal, just overload. The physio etc that looks after her needs to understand what and why those loads are being problematic and then to work out a solution.
It a really interesting topic and needs a physio who works in that area. See who is milling about the local training areas as there's bound to be a physio there somewhere.
Perhaps also help your daughter to understand that gymnatics comes with 'pain'. As does ballet, rugby, piano etc etc. The human body was never meant to do those types of things in such repetitive ways. Therefore to undertake them in the first place means that pain will be part of the package (not that much of it can't be avoided).