Do you have a male that she can see in plain site and if so is he building a nest? if not then that may be why. Every once in a while when a male wont build the nest or is being slow at it the female will help out with the process i had 1 male and one female in there own tanks but they could see each other and the male wasnt great at making nest but the female made one i was suprised. I then but them in my spawning tank and the female made most of the nest her self.