Could you post a picture of her? Sometimes mollies don't get very big so it is hard to tell how far along they are. A short video would be better too, I can tell you if she's laboring...maybe. But if she's sitting around at the bottom, not swimming too much, she could already be in labor. Sometimes they make you think they are and then hold for a few more days though. =) I had a molly go into for sure labor, and then just stop! Then she didn't give birth for another four days.
Be very careful when you move her, if you have to chase her, it's best to leave her be or she could get stressed and either drop the babies prematurely or reabsorb them into her body. I like to have a nursery tank to put them in over using a net, but I DO use the nets sometimes, especially if I already have fry in the nursery.
It really depends what kind of net you have, if you have one of those plastic breeder nets with a divider, you can add some plants to it to make her more comfortable like DragonFyre said. However, I still wouldn't suggest leaving her in the box more than, say, overnight if you want to put her in there before bed. If you do it during the day, I wouldn't keep her in it more than six hours, even with the plants.
The mesh net ones do have more room, and you can add some more plant stuff and leave them in there longer. But I wouldn't do it more than 24-36 hours or so regardless. Make sure if it is a net that it's nice and tight to the frame, otherwise babies can get stuck and be mushed in it(I've had that happen, but it doesn't very often. Just be sure not to poke or move it while babies are in it).
I like to wait until I am sure they're in labor before putting them in the net. Sometimes it's hard to tell, so you could wait until you see a baby to move her into the net with it. They can be hard to catch in the main tank, so I like to use a turkey baster. lol If you do that, make sure to be gentle when letting them out of it, otherwise they can get too much pressure and not handle it well, but so long as you do it gently the babies should be fine, I've never had a problem with that.
The nets are also difficult to let the mothers give birth in, because the babies can get eaten without a divider in there, but if you have a lot of plant stuff in it, most of them should be ok. Especially if you put some thickly mushed up plants around the bottom half so the babies can get in, but mom can't. I like to use those Anacharis
(I think that's right), viny plants in there and coil and knot them around in the bottom half, the babies get under or in it and hide, but mom can't do it quite as well. There's still a chance, but it is a little safer. =) You could also add a leaf in from a larger plant, the babies can get under it and hide, and if mom is busy in labor, she -might- not go digging for food.
Ah, here's a video of my Silver molly when she started going into labor. This may help you figure it out! But all fish are different, so yours may act a little different than this, but should have similar signs.
Oh I love baby fishies! Raising them is so much fun. Good luck to you!
*Eidt* Oh, I forgot to mention, sometimes mothers tend to get constipated when pregnant and can give off the impression they're in labor because they hurt and are pushing in some quiet corner, so try feeding her some fresh cooked peas two or three times per week to lessen the chances of it happening. =)