Dogs don't understand maternal/paternal relationships. That is, after they reach a certain age, a female no longer views their offspring any differently because of kinship. So, in adulthood, a mother doesn't see her female offspring any differently than an imported female.
So the long and short of it is, it depends on the females in question. Female/female combinations tend to cause some people more grief than male/male or male/female. I have two females (who happen to be mother/daughter) and I don't have any problems at all. I know alot of boxer folks in the same boat, and most (not all) have peaceful households.
