Your problem is that she is in the breeding trap.
This puts a lot of stress on the mother, which leads to her "putting-off" the babies untill she is out, or even aborting them.
Do you have a lot of hiding spots in your tank? My platy gave birth, and the strongest fry are now always hiding in plants or under my driftwood, coming out every so often for a few seconds.
And the Ghost Shrimp; no. They will catch any baby fry that swims by them and eat them. Other shrimp (like Cherries or Amanos) should work.