When to remove the mom?

[Donna Anastasi]

Blossom (mother gerbil) is housed with her 2 six week old pups (one male
and one female).  The father was removed before the birth of the pups
and Blossom is NOT pregnant with a second litter. I would like to keep
Blossom with the pups for a little while longer, but am afraid that she
might get competitive about the male pup and harm the female pup once
the litter approaches maturity.  My question is:

At what age (of the pups) do I need to remove the mother from the
litter?

Thanks!  Donna A.