I hope you're not considering moving her into the cycling tank. I would never use a breeder trap either.
I would leave her alone. If there are hiding places for her and the fry, it's much better to leave her alone than to take her out when she's so pregnant. And in any case, platies can have lots and lots of fry at once, it's not like you will want to keep all of them. The way I look at it, the fry that survive in the main tank are the strong ones - natural selection on a small scale. I get a little sad too when a bunch of fry are born, and then I see them slowly disappear - but do I really want each of my females having 10-20 fry once a month and keeping all of them? Usually one to 3 fry survive from each batch, and even that is plenty for me.