Part of the problem is that you've about 12" (adult size) of fish in a 5 gallon tank. I'd recommend getting at least a 10 gallon and cycling it (with BioSpira if possible). Then you could use your 5 gallon to raise the fry in.
Also, the breeding traps often cause great stress and will cause the livebearer to abort the fry or hold onto them longer.. but they can take 4-6 weeks to drop the first batch so she's not ready yet. When her stomach squares off and you see little black dots in her stomach (depending on her coloring), then she's getting close.
Just keep her there if her belly is large, she has a black spot neer her analfin, she must be close, I've just hesitated to put her in the breeder and she had babies overnight and were all eaten. Take my advise and keep her there she must be close