Sea_Monster,
I didn't get the same impression about your question as CFC did

I hadn't read you thought Molly's were egg layers, nor you hadn't read the post when you mentioned gravid spots or females looking square.
Maybe your female just ate and got fat, then did her b'dness. Or, she had a baby when you weren't looking, and ate it.
I have two female Platties, and on my colorful females I cannot see her gravid spot, so I watch how fat she gets. But with my silver platys, I watch her gravid spot and how fat she gets.
I am sure it is similar for Mollies, Patties and Guppies, except watch the tummies if the female is colored, and make sure you check before feeding (that helps me). Also, birth turn around time can differ between species. I read, somewhere that Mollies have a 45-60 day turn around for birth. Where as for Guppies it's around 28 days.
