Yes, it's pretty normal, as she is brand new to this "pack," for lack of a better term, and is trying to figure out her place in the family. I would watch her and if she doesn't start eating by Monday, a vet trip is definitely in order - in fact it is in order anyway, of course. Are her gums nice and pink and healthy-looking? If she has pooped at all, are ther any worms present?

Thankfully I am sure your older tow have their vaccinations, and you already mentioned they have been neutered/spayed. Watch their interactions with the pup, and just be prepared with a spray bottle of water if things get too rough.