I think you have enough duckweed in the breeder. I would say within 2-3 days she will drop since she hasn't already. I would keep the temperature constant or maybe raise it a degree or two. Otherwise, let nature take its course, your patience will pay off once you see how many babies that big girl is going to have. I would suggest letting her have them in the breeder and then taking her out once you see a good amount. She may have some more in the actual tank but they may hide and come out and you can net them and put them in the breeder with the others or they might get eaten but as long as you think she is pretty much done, then I would take her out of the breeder so you can save a good amount of fry.