A lot of hair removal products say diabetics should 'seek advice' or even avoid it. A lot of the time I think they are just covering themselves legally.
In practical terms, as in, should she use products like that, I think it's a question of using common sense. If your daughter has sugars up in the sky and finds she heals slowly or gets infections, then obviously adding to that risk is a problem (shaving, buffing, all of it). If she heals fine, then she'll be fine to use the product.
The other reason they say be careful is in case of neuropathy. Again, it's common sense. If your daughter has lost sensation in her feet or legs then she might not notice that she's damaged her skin, and so must take extra care. If she still has normal sensation then it's not going to be an issue for her.