Your Female Guppy
Hello kate...
You can't tell for sure. She'll drop when she feels the water conditions are just right. You can help by changing half the water in the tank every week and make the new water a bit warmer.
Next time, don't put the fish in a breeding trap. It's very stressful and can delay things. Just leave the female in the tank with the rest of your fish and start feeding all of them more often. If possible, start feeding some frozen foods like brine or mysis shrimp. Just chop up the cubes and drop them into the tank.
Adult fish will go after the fry if they're hungry. If they're well fed, they won't pay the fry much attention.
Another thing. Get some floating stem plants into your tank. This will give your female and the fry a place to hide and the thick growth at the surface will make her more comfortable. The two best floaters are Anacharis and Pennywort.
B