Since she is young and has not been handled much on that side, I would guess that it is not an eyesight problem but if you are concerned about it, then have it checked. Yes horses tend to get comfortable on one side then you move to the other and it is this whole new thing and they are not sure what to think. I think it is fine for her to look at you with both eyes at first. Soon, she will find out that you are not going to hurt her and she will relax enough to straighten her neck and just look with one eye. Just give her time and let her absorb what you are showing her. Sounds like you are doing great. Keep up the good work.