mousy lioness 

A very insecure person, male or female, who will throw you under a bus in order to get attention on themselves, and who needs to feel that they can do anything better than anyone else in the group.

Did you notice that Kim complains about everyone on our team, and how badly they do their parts of the project?

Yeah, but she can barely handle her own.

She's a mousy lioness, always putting everyone down to make herself feel better.

Haha, a mousy lioness. That really desribes her.

mousy lioness by not a dummy May 11, 2012