Hi, thanks for using Petco Pet Education Center, formerly Petcoach! Poor Mama! She is super cute!
I would take Mama to an Emergency hospital and have her looked at as soon as you can. Anytime there is concern for breathing it could be life threatening, especially if she is also weak. Puppies can suffer from low blood sugar which can make them weak. The fast breathing could be from a fever, pneumonia, or pain. The distended belly may or may not be related. She could just have worms.
The best thing for Mama is to have a Vet do an exam. I hope this helps and I wish Mama a speedy recovery!