Welcome to Yorkie Talk. Congratulations on your new addition, Millie.
My Max wasn't a big eater his first year. We ended up hand feeding almost all of his food by having him perform tricks for kibble, or by putting kibble in the Kong toy. He also enjoyed a food reward after walks or grooming. Now he is a chow hound.
Wishing Millie a good 12 week checkup with the vet.