I am sorry that this has to happen but I think the kindest thing you could do is turn her over to a reputable Yorkie rescue organization. They really do have the best interest of the dog at heart and can find her the perfect home. I know United Yorkie Rescue has very strict adoption policies and so you would know your little one would be going to a quality home. I would imagine Small Paw does also but I am not familiar with the organization.
Unfortunately there are a lot of people who can say the right things and you could adopt her to a home that you really don't know much about. A rescue organization knows how to weed out people who could potentially harm the dog and I know this is important to you. They do home checks and ask questions most people would not think about. You have to be so very careful as there are people who adopt these little ones to be used as bait from owners because these evil people know how to pull your heartstrings and say what you want to hear.
United Yorkie Rescue
http://www.unitedyorkierescue.org/faq.shtml
Small Paw Rescue of Houston
http://www.petfinder.com/shelters/TX540.html