She's definitely pregnant you can see this because of the gravid spot (the black spot she has) just before she's about to give birth her abdomen will be in a square shape, if your tank has a lot of plants and ornaments the strongest fry will survive hiding in those places until they are big so that the adults won't eat them
I'd say a week or two due to the fact that when she's close to giving birth you can sometime see the eyes of the fry