I'm going to butt in one more time:
I'm not a fan of leasing. Maybe I'm stingy, I don't know. But I would be very worried that the other person wouldn't take care of the horse as well as I would like, or make her degress in her training, etc. I think, from what you've said, that you're already meeting your pony's needs. So in my opinion, you don't NEED to lease her, and I don't want you to feel pressured into it because of this forum. It's still your choice though! Good luck with everything! You have an adorable pony!