The minimum tank size for a Mickey Mouse Platy is 15 gallons or more and should be well planted (some will tell you 5 or 10, but I disagree as they are better off in groups). What is she in now, and why do you want to move her, unless you think she's breeding? I'm a bit unclear.
If she is breeding, it takes about 30 days for fry to emerge. They are a livebearer and will have about 40-60 fry. You will be able to see the fry in her belly. If you think she is going to have fry, this link may help:
http://freshaquarium.about.com/od/li...ickeymouse.htm
I think you should also be feeding her a mix of vegetables or herbivore fish food as well as the flakes and worms.
And what would you do with your betta?