Well, she will run into issues with patterns. There will be changes she will have to make.
So, I do see the point in making it a topic, just to find out if she does actually know about the change (she may have just learned that way without knowing).
Knitting is a very ambidextrous craft (other than crochet or stitching for example). It is not much of a problem for a lefthander to learn standat knitting and not for a righthander to learn "the other way around". Pay attention to both your own hands when knitting!
But like a lot of things we can do them best the way we learn them.
I would start to chat with her. When and how did she learn knitting? IS she actually lefthanded?
Then you know what she does and why. Tell her, that if she uses this method there are changes to make. You can offer her to help finding instructions (and we will help you with that )
If SHE gets to the conclusion that she wants to try it out the other way, have patience with her. But do NOT even propose to her to re-learn.
I type with all fingers of both hands (my way). And I am fast. If I would ever learn true 10-finger-system, I would probably suck for very long and as a result not be any better. I do know what I am talking about. Standart is great but if something else is your way: Stick with it.
We actually had a discussion with a left handed user lately. It is here: