EDIT: Changed her structure a bit back to what it was. /shot. That is all. /edit
A few really quick sketches and scribbles to give you an idea of how her hands work c___c I imagine when she does things like drawing, she puts the pencil between her inner thumb, pressed against her inner forehoof. Or if you think more people-like, between her inner thumb and both forehooves. Or you can do all four fingers, depending on her habits because there is more than one way for a person to hold a pen OTL But I'd imagine it's pressed against the flesh and not her actual hoof, as there's no traction and it would slip around.