I would strongly suggest not putting her in there, it may be big in terms of boxes, but it's still a very small space as far as the fish is concerned.
Do you have a male molly (whether balloon or not)? Has the female been in the same tank as a male in the last 6 months? If yes, then yes she is, and so is the other female.
And yes you can just stop feeding them, fish can go over a week without food with no ill effects.