She is pure evil. She is determined to ruin my campaign and the fun for everyone else. This is not form her being in character, she is just sadistic. And creepy. And violent. We shall call her Evil Shrew. Examples of her malevolence:

Me: You enter the vast hallowed hall of the Cathedral Helm. If you present yourselves respectfully you may just get passage to Maztica...
Evil Shrew: Veronia strips
Me:

Evil Shrew: (Interrupting romantic scene between two characters, Andre and Amra). "She used to be lesbian". Veronia says as she pushes Amra aside and forcefully kisses Andre.
Me:

Me: A piece of paper flutters on the breeze...
Evil Shrew: Veronia throws it into the fire.

One day, I had had enough. I told her to leave. Then, three things happened before anyone knew what had hit them.

A) She attempted to punch me.

B) Somehow a cardboard DM screen saved me from serious injury.

C) She grabbed my Forgotten Realms Campaign setting and ran.

She returned it by throwing at the back of my head at rehearsel for a play our school was doing, the Elephant Man.

The characters Andre and Amra got back together because Andre still loved her and thought it was vaguely hot that she was bisexual.