Actually, you should give it to your trainer, it's very nice. You've come a long way, if you compared this to your horse drawing from before. And the eye's so dark BECAUSE all you had was a 3B - that's a pretty soft lead, so is very dark. If you do add a little background (can be vaguely hinted, and give it as a gift, be sure too spray it with fixative - because 3b is so soft, it'll rub off easily.

It isn't perfect (you and know the artists sees things in his or her drawing that others never will notice) but I bet she will think it is!