Co-Worker Cussed Me Out Today~?

I work in an office where my co-worker is related to our big manager. Well, today, I heard her on the phone with a manager saying something that I didnt say. She hung up, and I confronted her and told her I didnt say that. She went balistic screaming Gd and telling me she was tired of me being so nosey. (hello, we work in cubacles and we hear everything). We do have an immediat mgr above us, if I bring this to light, her relative will take up for her, so I am kinda screwed. What would you do? She gets away with everything because her relative is our big boss. She says whatever she wants to say, and she never gets in trouble.