To figure out dominant eye, just have her hold her index figure upat armes lengthand close one eye at a time. The dominant eye will keep the index finger in the original position and the weaker eye will appear to move the obect to the dominant side.

I am right handed but left eye dominant, I use to be able to shoot both ways but required a closed eye to shoot off the right and it caused accuracy to decline. It always felt more natural to shoot left, so i just went with it. In terms of shooting and hunting, I like both eyes open.

If she is more comfortable shooting off the right side but left eye dominant then try and train her. If vice versa go with it, let here be a southpaw. Of course assuming she is in fact left eye dominant. Personally think feel is very important to shooting success which leads to enjoyment. So let her deciede the way vs forcing her.