If you think that the best way to ensure that they are separated is by sending one to stay with someone else for the time being, then YES, that is exactly what you should do. You don't want any 'accidents' happening, especially at such a young age when it would greatly endager her life. She is WAY too young to have pups right now.
Off subject, but you said they'd been together since they were 6 weeks...is that how old they were when the breeder placed them with you? If so, that is VERY young for these little ones to be leaving their mom and litter mates. Most reputable breeders agree that 12 weeks is the safe age. Anywho...just wondering...
Welcome to YT!
