normally we suggest you start a new thread for a new topic, ie: pregnant mollies.
however, since it is here I can say she looks pregnant.
all female livebearers that have been in a tank with a male anytime during the last 6 months can be pregnant. This is because the males leave sperm packets in the females when they breed. The females can then use the sperm packets at a later date, anywhere up to 6 months after they mated.
The gestation period is about 1 month. If the fish has been that fat for more than 2 months it probably has worms.
Do not bother moving females that are really fat because you can stress them out. If you want babies then move the females into their own tank before they are huge, and have lots of plants, especially floating plants like Water Sprite in the tank.
Your female is not huge but is big and if you have to move her at this stage, catch her with a net and bring her near the surface, then use a small container to scoop her out with some water, and then move her into a new tank. Otherwise leave her alone.
Any tank you move pregnant females into need to have the same water chemistry and temperature as the main tank, and have a filter and contain at least 20 litres of water (preferably more).