Pregnant Molly?

I have a 55 gallon tank and have been adding fish to it slowly for a few months. The latest fish I got were mollies. Recently after I got them I noticed one kept nudging the other. I looked it up and figured out they were a male female pair. The female's stomach is starting to enlarge. I think I see a gravid spot but I'm not positive. Should I prepare for her to have fry?

Yes,
when the stomach takes on a \_/ shape then expect fry! yours is well on the way

Thanks, I have a nursery tank set up already. I bought a breeders box but the holes on the bottom are pretty big. Its a top fin two way breeder. Have you ever heard of the fry falling through the holes?

This is her today. How long until I should expect fry?

How close is my molly to giving birth?