I would really need to see what she is doing. Most of the time, except in the case with dogs that lack a desire to work with their handler, the dogs get bored and lose drive because the handler/training is boring. Does your friend use a lure so the dog is working for the reward or do they pop out the toy, give food/praise, at random times (I tend to use it for best effort or if I know the dog can go flat in a certain sport) so the dog is working to earn the reward? There is a huge difference. Too many trainers do the former (which is why crazy toy driven dogs are favored in OB) instead of the latter. If done right a dog should build drive and get pushier throughout the routine.
I would crate the dog before training and afterwards. Otherwise, no, I do not believe in creating drive through deprivation. There are better ways to achieve things.