New puppy doesn't smile or wag her tail

Roo is 14 weeks old, I've had her for 3 weeks. She's very mellow except for when she gets the zoomies. And she's really sweet and cuddly. But she doesn't wag her tail at all, and she doesn't smile like most dogs do. Especially Poms. It makes me worried she's not happy. Is this normal for her age? Will she grow into a more expressive personality?

I had a pom for 11 years who was happy and wagging all the time. I'm not sure if I'm doing something wrong with Roo. I'd like her to feel safe and comfortable here.

Any insight? Thanks