Hello! Welcome to YT!!!
I'm sure your boyfriend means well by thinking he wants to breed her, and he probably knows how expensive Yorkies are and thinks you guys might be able to sell the pups too, but please just get her spayed. Go to the Breeder's section on here and you'll find stories about mom dogs who need C-sections (expensive emergency C-sections, especially if it's needed in the middle of the night) and those who have lost puppies or even mom. You don't want to put your little girl at risk like that. Yorkies don't have easy births, which is part of the reason (besides popularity) that Yorkies are so expensive. They usually have 1-5 babies, not 10 or 15 like big dogs do. What if mom rejects the pups - are you willing to stay up all night bottle feeding? There are so many unknowns that it's just best to leave breeding to the breeders. If you are interested in breeding then do some research and speak to other breeders and when you are ready you should buy a girl to breed. There are medical tests you need to do and you have to know the pedigree and what "faults" the dog has and how to select a stud to minimize those faults. Just enjoy your little girl and don't try to breed her. Too much can go wrong.
You might get some nasty answers on here so be prepared. I don't usually respond to these posts but I thought I would explain why it's not a good idea rather than just tell you not to.
