Wat you should do is put her in another tank or a jug or somfin with some water (with a bit of salt) though float the tank your sick molly is in so she stays at the same degrees or fareinheight as the other fish so if u return her she doesnt get to hot or to cold and if the saltwater doesnt fix...
Yes, it doesnt matter if you put a male sailfin mollie with a female baloon mollie theyll mate... mollies are all the same breed but look different because of the adaptions they had to make in the wild...
I agree with Anastasia to many live bearers will cause you havoc... Oh and orkybetta i got a betta just like your male him and my female have just given off there 4th bunch of babies...