First, she turns invisible

Camilla looked at Peter's family. The sight of the life her ex had built without her fueled her with rage. She hated every single one of these assholes. For a moment, she considered lighting them on fire with a mere gesture of her hand, until nothing remained of them but pathetic piles of ashes. Then, all she would have to do would be to erase any trace of their existence in Peter's mind and become his wife. She shook her head. No. This would be too quick. She had prepared her **** for years, and she didn't want to waste it.

-Look at me, she told the rest of the family. When I snap my fingers, you won't be able to see me anymore. I'll be invisible to you, and you'll forget you even saw me.

Camilla snapped her fingers. She smiled when she saw a confused look appear on the faces of this family, as they were obviously wondering who they had been talking to.

-So...who was it, darling?

-I...I think it was someone who got the wrong door.

Camilla struggled not to laugh, as she saw Peter close the door. She was inside the house now, ready to mess with their lives without them suspecting her presence.