Bought two female swordtails for cycling and ones pregnant?!?

These are my first fish since a betta tank. I have a very sentimental little sister that didn't want me cycling with danios and then returning them. I wanted guppies so the pet store had me use swordtails insteadof danios to cycle, but I think one's pregnant. She's much hungrier than the other and poops more and has a swollen abdomen. Oy. What can i do to support her? cycling is bad for them already and I know they die after birth anyway. My water levels are good and i seeded the tank a few days before I got the fish.