Livebearers breed like rabbits so be prepared for a lot of pregnancies. Does she have a large squared off body and is her gravid spot obvious? You should not leave her in there for any more than 48hrs as she will become stressed. She will give birth to them in batches (anything from 30mins-2days imbetween each lot). Does your trap have a place for the fry to fall into and some kind of floating plant. Fry swim to the surface when born so that offers some cover, otherwise the mother may well eat them. You will know when she has finished as she will be much slimmer, you must take her out then. You need to feed your fry 2-3 times a day on food which you have crushed into powder.