Nice bright portrait. A couple of things.
First - the pupil looks square to me too. I don't read comments before looking, so thought it was just me until I saw Duncan's comment above.
Second, the top of the head cut works best* when there's no dead space underneath. I like to get in really close, or have space top & bottom. There's no space at the top of the image, but lots at the bottom which looks kinda awkward to me*.
I'm also going to agree with Kodiak on the skin sheen. I'm really liking the bright lighting and lack of shadow - it works well for a younger subject such as this*, but the cheeks nose & forehead have just caught a bit too much for my liking. It's a very minor thing though. The head cut is far more distracting*.
Finally, I really like the pose. Slight angle to the shoulders, head lifted without seeming forced, engaging eye contact and a nice smile.
Really nice - well done.
*In my opinion. Please take what you like etc etc..