Hi juwanil,
I've had lots of experience with Zebra Danios. This is quite normal behaviour for your female, especially if you know she's carrying eggs. Danios can become quite terrtorial when "pregnant". If the danio is nipping to the extent that she isn't hurting any of the other fish, I wouldn't worry about it. But if she is, you might want to seperate her from the other fish for a while, maybe you can use one of those breeding traps, that you can easily find at your LFS. Good luck! And keep us posted!
~ Ali