Hello, Welcome to DogChihuahuas.
Great having you on board, look forward to hearing updates on the new puppy, and mum too.
Firstly i would like to suggest consulting your vets clinic, if you have serious concerns with the new puppy especially if mum isnt letting pup feed.
I personally have never had any litters from my chihuahuas, so unfortunately can not advise on
this, but some of our memebers have experienced this, so can offer they experience.
Regards
Sarah