Breeder saying a 4 and half week old rottie pup is ready to leave its mum?!?

My opinion is that you should turn her into the local animal control. This is WAY too young, and is cruel to these puppies. Pups that are deprived of their chance to learn how to interact with other dogs can be in for a lifetime of problems, not just with dogs but with other people. Good luck. I feel so sorry for those puppies and this "breeder" person sounds like a terrible creature.