Did you know that California has some of the toughest puppy lemon laws in the US? Since liver shunts are hereditary, Melody's breeder is required by law to pay for her treatment up to 1.5 times her purchase price since her condition was discovered within one year of her purchase.
California Lemon Laws for Dogs
Are you aware that Yorkies are 36 times more likely to be born with a hereditary liver shunt than all other breeds combined? Since you took a replacement puppy from the same breeder, the odds are very high that this puppy could have a shunt also.
I am not sure why you would even get a dog when you are "negative money". Even the healthiest dog costs a considerable amount of money over it's lifetime. Toy breeds like Yorkies are especially susceptible to pancreatitis, knee and other joint injuries, etc. What you will do if this puppy has a shunt or needs knee surgery for luxating patellas as so many Yorkies do.
Liver shunts are correctable with surgery. There is no reason why Melody should be put to sleep for a treatable condition. If you cannot afford to care for her, I urge you to relinquish her to a Yorkie rescue group where she can get her surgery and find a family who is able to care for her.
Since the other puppy isn't even paid for yet, I would also urge you to rethink having a dog at this point in your life.