Congrats on your new addition.
This is a big day for your little one!!! I think 8 weeks is a little young to leave the nest, but.... She really should have a chance to get to know her surroundings smell and see everything, then introduce the other pup. Don't be afraid to get on the floor. We are very big to them and we have to get to their level sometimes to earn trust from them. I imagine she is scared to death, she has left her comfort zone. Have patience and introduce her slowly to things... Her snapping is coming from fear... Every puppy has their own personalities and this is her way...
If you haven't already try to hand feed her. Do this on the floor with her. Don't over feed the nutrical, you can give her diarrhea and that can dehydrate her more. I always keep pedialyte on hand. Also changing her diet can cause the same effect in the small ones. I seen her picture and she is a real doll. I know you want the best for her...and it can be a little scary, but she will come around....