Oh my! What a surprise!
I'm glad Gabby is separated out from Gigi and her litter.
It is safe to leave mum with her babies until the babies are 4 weeks old. It is at that time you should separate the males from the females. You can tell the sexes from 2 weeks old (the earliest it is safe to touch the babies) but the babies should stay with their mum until they are 4 weeks old. They need to feed from her and learn how to be a hamster
Don't touch or disturb the mum or babies from now until the babies' eyes are fully open at 2 weeks old. I'm glad the breeder is taking the babies back.
Although I wrote this about Chinese hamsters, the principles are the same for Campbells too:
https://vectishams.com/chinese-hamster-litter-care/