I'm going to get out of work 15 min late and not tell the person picking me up.
Why not tell her you'll be 15 minutes late?
I don't want to deal with her. I hate her.
Regardless of what you think of her it is rude to keep people waiting. You should give her notice that you'll be late.
Whatever...
I don't think you'd say whatever if she was picking you up 15 minutes late.