What could be causing this?

[Detweiler66]

So my family had puppies and I gave my girlfriend the baby chihuahua mix that's short hair and blonde with a white strip in the middle of her head and she got fat and stuff and she's 9 weeks old and she keeps shaking her head and then foams out the mouth and then throws up she also has diarrhea and and lost so much weight we de wormed her way before this happened and she was fine so what can it be I really don't want my girlfriend or I go through another loss of a dog and this one I told her can be 100% all hers

[Kori1236]

Unless people on here are vets no one is qualified to answer this question. Even a vet can only speculate online. Take puppy to the vet to figure out what’s going on, could be anything from genetics to parvo or distemper