I would be a stress piddler also if I have lived her life, she has probably been crated most her life, it takes a lot of work and patience to gain their trust to stop this behavior, I had a recsue that did this, about 3 months, and if all your going to do is breed her and then sell her she will be worse, why don't you allow someone that is willing to give this precious girl a chance in life and work with her a chance to get her now.
If you have never bred yorkies before, its more than throwing 2 dogs together, you have to help whelp in some cases, up for days, a do whats best for the yorkie, I don't mean to be or sound rude, but pls find this girl a home that will be willing to keep her no matter what. Sometimes you have to take yourself out of picture and do whats best for the yorkie.