When I was 4 I was diagnosed with 3 different forms of arthritis - juvenile rhemetoid, osteo and the third I don't remember - and my parents were told that my activity level was to be restricted. I eventually got used to the chronic pain and resumed my life. When I was 15 the diagnosis was reconfirmed by an arthritis specialist and the restrictions imposed included not walking more than 8 blocks/day, no gym class and no high impact sports of any kind. Up to that point I had played volleyball and softball, which immediately went out the window. Throughout all this, I had gotten to a point where because I was in constant pain I got used to it and lived with it. Apparently this has caused me to have a high pain threshold for somethings but a low one for others. Even today, I have to really listen to my body when it comes to joint pain - I tend to take it seriously when I "feel" the pain in my knees or hips as I'm used to those areas having chronic pain.
As Enna says, watch your DD - she might think it's okay to do something because she doesn't feel the pain but she could be doing damage just because she has gotten used to not being pain free.
Lots of prayers and pixie dust that things work out in the end for her - and you!