Advice for Zebra finch breeding?

I have three finches in one cage. 2 are female sisters and the other is a male from another clutch. There is 3 eggs in the nest but all 3 of the birds are taking turns. One female isnt staying in it much so I dont think they are hers. What should I do? If I take her out will she be ok by herself if I put her next to there cage? Need some tips. Also the one I think is a female that didnt lay the eggs I wasnt ever sure of her because she is solid white and her beak is not light orange but not red either. Also my neighbor wants some from me so I dont want to pull the eggs out and toss them.