No doubt. I know some offer definition adjustments, but others don't. Even if she takes the offer to upgrade to the 50GB plan, she'll still have to be careful and watch her data.
I think that even if I had unlimited FIOS or something I wouldn't watch a lot of on demand programming. I find it hard enough to find the time to watch what's on now. LOL. Maybe an occasional movie, but I could do that now. I received some tokens for something and it's enough to watch a few high def movies, but again, I have enough to watch for now.
You can go there to find out how.
That's just for Netflix. Other services have their own ways, but you normally have to do it at the provider's end, not at yours.