I have read in countless places that mollies won't eat their young or the fry of other mollies, but from my experience that is completely untrue.
I have a quaranteen tank, that I put 5 new mollies in and just checked again today and saw two fry swimming around. Scooped them out and have them in a small 2 gal
. From the other time my mollies have had fry, they have never had under 20 fry at a time. I have some hiding places in the QT tank but only have two fry left....so the others must have gotten eaten.