If she is pregnant, you can take the advice of many others here and raise the temperature overnight, meanwhile providing an extended period of darkness. If you want to take it further, refrain from feeding her for a day or two. This is suppose to induce her labor.
If she is sick, I don't think there is anything you can do (other than green peas ?). I've heard of a scenario where the guppy female wouldn't release the fry & got really big. It got to the point where she expired & the breeder conducted a cesarean section, to retrieve the fry. I certainly hope this is NOT the case and your girl will come around very soon. I'm surprised mollies get THAT big during pregnancy. Whew!