How long have you noticed her being pregnant? When her belly starts getting a box shape towards the anal area and her back area starts showing its expanding out. Seperate her, preferably in a 2 way breeder box. She will eat the fry otherwise.
She still has a little but. Just make sure you keep your water clean and have her on a good diet. The more stuff she has to hide in to feel secure, the better (plants, driftwood, etc). It's not uncommon for them to stress to the point they pop early with a bunch of dead fry. But also be preparred for more fry. Mollies retain the males sperm for up to 6 weeks, if not longer. Good luck to ya!