I would say she is pregnant, yes. Usually with pregnant livebearers, you can see a darker spot/patch around the anal fin called a "gravid spot" (shown here with this female platy) that indicates pregnancy. Not sure about how far along she is though. Some say that very close to birthing you can see little black dots within the fish that show off the eyes of the guppy fry.
Best of luck, keep us all updated!
She could be doesn't have to be. Yes, she shows a gravid spot. But also non-pregnant females show a gravid spot. If she's pregnant, than she's still got a long time ahead.