I feel like a broken record...for those of you too young to know what that means...too bad! anyway:
If the Chinese quail you are referring to are Blue Breasted aka button quail then they are better off in single pairs. This is why they are not excepting the 2nd female/hen. If you are referring to another type of quail, I notice on here that owners say they are best in groups of 3-4 hens to one male/cock. If they are buttons I would remove the 2nd hen and get her a mate in another enclosure or if the one you are using is large enough with hiding places you can try to keep 2 pair in one cage. I do not recommend this though...but others do with little to no trouble.
Good Luck.