I want to tell you the story about my Jada. She was a breed dog for a questionable breeder. The breeder went against the advice of our mutual vet and bred Jada when she was a little over 2 years old and about 4lbs 5ozs. She had a singleton and had to have an emergency c-section. Our vet convinced the breeder that she would always have problems as she was too small and she did agree to let him spay her while she was under anesthesia for the c-section.
The breeder then told our vet that since she wasn't able to breed her again to find her a good home. He immediately thought of me as he knew I would make a good mommy. The breeder rehomed Jada to me when her pup was only 6 weeks old.
She is the love of our lives and a very spoiled little princess now and I cry when I think of what she went through.
Your little girl is smaller than Jada was and is carrying what your vet thinks is 3. I would be terrified of even thinking of taking that chance. And I don't know of a vet with any sense that would recommend a breeding based on a male being "cool" Poor little baby