She appears to be. I wouldn't move her that will cause complications if she is ready to drop fry. Your best bet is get some floating plants in your tank for the fry to hide when they come out. You will probably lose a few but eventually you will see some in the floating plants and also check the top corners of your tank. Then when you see some use a turkey baster its much easier than a net and less stressful IME and move them to your breeder net or another cycled tank depending on where you plan on keeping them. Good luck!!
If she is - it's very early, do you have males? has she been exposed to males? You'll know shes pregnant because she'll develop a spot, if you look at the side shot of her, right on her abdomen in front of her Mickey mouse spot and behind her pelvic fin- Its called a Gravid spot all pregnant livebearers get them. When shes ready she'll "square off" she'll get so fat she looks square! not funny but kinda when you separate her, if you can use a breeder basket try to go that route but put a floating plant in it for the fry to hide in cause momma platys don't mind snacking on their fry. plus it makes the fry easier to collect when shes done. Good Luck to you Great photo too!
Yes, that female is pregnant. She is probably a few weeks away from dropping, though. A separate tank is better than a breeding basket for dropping/raising the fry. Fry raised in breeding baskets tend to be very slow growers, often stunted. Sometiimes the basket will even kill fish by accident. A breeder trap allows the female to drop fry, which then go through an opening into a larger space, such as another tank. But even that can sometimes stress out the female, causing premature drops.
I prefer to isolate a female in a reasonably sized tank at least a week or two before she's likely to drop. I load at least half the tank with Guppy Grass or Hornwort, and add an aged sponge filter. For a Platy I would use a 5 or 10 gallon tank. Cycling is automatic by adding the large mass of plants. I know this does not agree with what you hear about setting up community tanks, but this is not a community tank.