Dena,
I am so sorry that you are being forced to make this very sad choice.  Have you talked to the breeder?  I know that she doesn't really owe you anything (you stated this all came about on its own) - but maybe she would take her back and get her better again?  I just hate that you have invested so much love and emotion into little Zoie and then the 6K and in the end you will just wind up with a whole lot of sadness.  Dena, I am so sorry. 
