I'm not a credentialed music educator, so perhaps I have little to stand on when it comes to this question.
But here goes.... Stick with SMN. It opens every door. The more she uses it, the greater ease she will have in making music, wherever her future interests may take her!
As a shape note singer, I find that anyone who knows SMN can sing shape note with relative ease, but not the other way around. As an 'aspiring' HD player, I find that nearly every book I buy has a different individualized method of notation.
MD tab is at least a standardized and widely used system., but there are others, too. For example, there's the abc system that fiddlers often prefer.
Any or all of these are things she can (and will) figure out on her own.... Translating them in her head into SMN!!!!!