I worked with an agency RN when I was a GPN at a LTC (lotsa' initials there, lol, didn't look right). She once called the sup 18 times in one shift on me, for such things as leaving the med room unlocked, keys on top of the med cart, etc. These were lies on her part, and when the sup came down to investigate, she found out that the door was locked, keys in my pocket, etc.
I initiated a talk with the RN, in the med room, away from any other ears, and asked her what the problem was. She was flabbergasted, and denied a problem, as well as denying calling the sup, but believe me, once she knew I was on to her, the reports stopped!
Best of luck, hope this helps.