Welcome to the forum. The Nemex ( Pyrantel Pamoate ) is a goog wormer for Bitch and pups. I always worm Bitch and pups at same time. There is good information on the forum health section here at Beagles Unlimited.
Feeding Bitch all she will eat 3 times a day is good also plenty of fresh water. Try to feed your Bitch the best quality Kibble you can. (not grocery store type kibble)
If Bitch weight loss is severe you may need to get her checked by your Vet.
What puppy food are you feeding and are pups still nursing?
A little more information on Bitch would be helpful. Also, is this her first litter of pups?
As for pups vomit , do not over feed at one time and make sure puppy food is room temp. (not warm)
Give pups water in shallow dish no more than 1/4 inch deep.
Post back and let us know how things are going.