She's gravid for sure, and if
@emeraldking says so, you can trust his word, he's a livebearer authority
Plus you have males in the same tank that are courting her in the photo by the looks of it, so it's only a matter of time. How many male mollies do you have and how many females?
When you say you want to be prepared for when she has her fry, what do you mean to do? Because some methods, like moving the female to a breeder box when she goes into labour can cause a lot of stress and even injury to the female by being netted while so heavily gravid, and stress is never good in any species during labour.
But there are other things you can do that help give the fry the best chance of survival. Some use a separate breeding tank, moving the female to that tank to birth then removing her after -if you wanted to do this, it's important for the other tank to be cycled and prepared, and to use a container like a jug to catch and move the female inside the jug of water, rather than lifting her out with a net.
Or you can use a breeder box/net/tank, but only capture the fry after birth and move them to safety then. Again, there are tips and methods to give you the best chances of saving them all, like checking the tank first thing in the morning for fry hiding at the surface plants or on the substrate, and using a torch to see, catching them before the other fish are awake and alert and likely to eat them.
Adding lots of dense floating plant matter is probably the easiest, safest way to give the fry the best chance of survival in a community tank. a load of elodea, water sprite, guppy grass, hornwort - cheap, easy to grow stem plants that can form a dense little thicket. The fry will naturally head to a load of plant on the surface like that, and can navigate around it to hide from hungry adults much more easily than the adult sized fish can. You can feed the adult fish on the other side of the tank and the crush some food very fine for the fry, and give it them directly in the plant "nursery" so they don't have to risk venturing out among the adults for food. Once the fry are a few weeks old, they'll start to swim out in the open on their own, as they know they're now large enough that the adults can't eat them.
If you let us know what you'd like to try to do, we can share more tips
As an adult it's a lot of fun to raise livebearer fry (for a while at least, the numbers do tend to get overwhelming after a while!) but it's also a great learning process for kids.