Molly pregnant or sick?

[Bree2000]

Hi there About a week and a half ago (maybe 2 weeks) I purchased a Molly from the pet store. This is my first Molly and it is kept with my guppies and neon tetras. I have noticed that her stomach has gotten very bloated looking. After doing some research I found out that it could be that she's pregnant (if she's a girl haha) or sick. Is anyone able to help me? What's should I do? I have attached 2 photos. One with a guppy when I first got the Molly and another one which I took today. Thanks in advance!