Whether sneering at your ideas or trying to take credit for them, your co-worker too often cuts your legs out from under you. Diane Gottsman, founder of the Protocol School of Texas, helps you stand up to these utterly undermining ways.

Take notes.
Keep a log of times your colleague takes jabs at you or seems to sabotage your work. Then take a good look at the incidents to gain some objectivity—is she really being cutthroat, or are you being overly sensitive to her criticism? Assess the damage she’s doing by asking other co-workers if they’ve noticed a pattern, too.

Take it outside.
An underminer loves an audience, but be sure not to give her one. Instead, pull her aside privately and address the issue directly. Maybe she’s secretly upset about something that is spurring her efforts to perpetually put you down. Clearing the air gives you both a chance to fix the situation professionally.

Take it to management.
If your co-worker will not correct her behavior, consider taking it to the top. Speak to your supervisor, offering clearly defined examples. Let her know your colleague’s attitude is not conducive to a positive work environment. Then let your boss reprimand the perpetrator’s inappropriate behavior.