If she is 45 days or over in her pregnancy she should be ok with worming and it wont hurt the babies as I worm mine before breeding and when they are over 45 days they get wormed again if they need it. Check her eyelids and see what color they are...if pale then worm her and if they are a bright pink its something else or she is putting everything into her babies is why she isnt gaining weight. I check the lids first and go from there. Cydectin is safe for Pg goats, also a paste wormer will work for tapeworms and I dont use Quest as its very tricky but some do ...I dont...check her first and then worm ...thats what I would do and also give her some alfalfa pellets or alf hayor some beet pulp as that should help with weight. Just dont overload her with feed if she isnt used to it. That can cause more problems. Good luck