Do you think that I should refuse to help and stop talking to my friend?
What does your friend want you to do?
Take her home!
Maybe you are the only person that she trusts to get her home safely. If you have the time, I think that you should just take her home.
I'm already tired of her. She should have a sober driver.
You are the person that she wants to be the sober driver, which means that if she is really your friend then you should be willing to help. How would you feel if your friend left you with no help?