This is the primary problem that someone with little experience performing the lift, let alone coaching it, is going to have. Everything's fine, as long as everything's fine. But if it's not...and I can't work out how to coach her past them.
The problem with your post is that I am limited by your (quite probably erroneous) assumptions and observations, because you are not experienced coaching within the model, and most likely not very experienced coaching human movement at all. Now, this may sound harsh, but it is what it is. I don't go onto guitar forums and try to tell people the problems with my girlfriends fingering technique. Because I'm not a guitar player, let alone a guitar coach. The primary evidence of this lack of experience is that you think that your description of the problem, absent any visual aids whatsoever, is going to be sufficient to A) figure out what's going on, and B) figure out how to fix it, and C) somehow instruct you in a way that YOU will be able to fix it.
It's just not going to work.
I can't see your girlfriend from here. Post pictures and video. It may be that you'll need to seek out a coach.