If it works for her that is fine and great. This bow hold will not allow her to play using the whole bow. If she plays below her right hand the bow will pivot over the strings. She can't put pressure on the lower third.
Also, there is no grip where she is holding it so the stick will wear eventually where she holds it.
I definitely don't recommend it, to begin with. She might be better off with a half size bow. This way of holding a bow makes the bow lighter at the tip but complicates other techniques.
That being said, what really matters is that she is able to accomplish what she wants to achieve.

It's common in areas/groups, where many learn from the same players/circles. It's fine if you don't use, or need to use the whole bow. Playing from your hand to the tip will be fine and even makes the weight of the bow towards the strings less/lighter. It's not fine if you from time to time need to use the whole bow or the frog of the bow. In other words, you are slightly limited and the bow is lighter. For some types of music, this is OK. However, there are more players playing any type of music using the more common bow holds than the choked up on the stick hold.
The same lightness of the bow can be achieved by using more pinky when using the standard Franco Belgian bow grip.
I would however never criticise anyone for holding their bow the way that works the best for them and they are able to successfully achieve a good and sometimes even great sound as well.