I think part of the problem is less the size of the horse and more the size of the saddle. It looks to me from all the pics that the saddle is just a bit too short and and this adds to the illusion of your height. As for horse size I agree with the others, horses are bought and sold for less reasons than that.
Here is where we as humans have to remove the emotional. Trust me I am fighting that feeling right now, as my husband and I have moved into gaited horses and have 3 QH/paints we need to sell as we aren't using them anymore. First of all our horses don't love us, they don't have that emotional draw. If they had those type of feelings they would never allow us to wean and sell their babies. We all tend to think our animals have the same feelings we do. They are much simpler as they require food, water, shelter and care. They are only concerned with their needs.
Look at it this way, by selling your girl you are allowing someone else the pleasure in owning a horse that you have trained.
A woman can NEVER have too many horses.....