#1- You must speak to the parents and be on the same page.
#2- Listening is NOT an option.
#3- Let her know that you EXPECT her to listen and that if she chooses otherwise, she will have a consequence.
Example: the next time she ignores you, stand I front of her, look directly into her eyes and say in a firm tone "I expect you to listen to me the first time and I expect you to respond to me when I call your name. If you do not do this, you will lose all television privilages for the rest of the day. Do you understand what I am saying?"
Eventually she will realize that you are not a doormat and that she won't get away with this behavior with you.