Well congrats on the new lil b.p. and I know what it's like to keep kids off a new snake in the house (we have 4 kids ourselves) but it's best for the snake. We just explained to ours that the snake was scared spitless of all of us and it wouldn't help the poor thing if we bugged it at first.
Sounds like the baby might be underweight (I'm no expert tho as we are still relatively new to balls ourselves) since I don't believe a well fed baby would appear distinctly triangular in shape. If she's taking an adult mouse once per week tho that should get some weight on her I would think. Just remember to leave her for a good 2 days after she eats before handling.
Hopefully someone with a lot more experience can comment on the respiration questions you have.
Welcome to the forum!
~~Joanna~~