i have this(as well as some floating plants and other hiding spaces) and it worked.. but i am not sure for how long. over the last couple of days i have discovered and caught six of my platy babies but watched many more come out from hiding and get snatched up by one of my four adult...
if you were doing everything right she may have just been a weak one to start off with.. hope lies in the fact that you can get more fishies.. good luck with your cichlids