Hi Aly, stretching can be tough for young dancers as it does involve some degree of pain, as a teacher I try and explain to my pupils the difference between "good pain" and "bad pain" in their stretch class, I also let them have the choice as to how far they push themselves as pain thresh holds vary!
On the topic of stretching at home, I encourage it, as stretching once a week/a few times before class isn't really enough to improve flexibility greatly.
For leg flexibility I normally suggest my dancers sit with their legs together in front of them and fold their chest over their legs to stretch the hamstrings and hold this stretch for minimum 30 seconds, then repeat the same with legs in a "frog" position in front of them (feet together,knees out to side) and then sit in splits, both legs and then in second (box) again for at least 30 seconds. If she does this every day, after a good warmup (very important) and under supervision whilst she's young, your DD should see a big improvement! If her splits comfortably flat then putting a folded towel/pillow under the front foot will increase the stretch! Hope this helps! X