I know you're probably looking for a profound answer (lol), but the best thing is to just point her to the Scriptures. Ask her if you can study with her; not necessarily that you'll only study the doctrines of grace. But, I assure you that it will come up in study.
Perhaps you can also show her the differences between historic Calvinism and Hyper-Calvinism. Hyper-Calvinism is heretical, IMO.
Make sure you are very gentle with her. All she knows about Calvinism is what her dad spews from his mouth. I'm sure they don't teach much at all about salvation at her WOF-ish church, so perhaps a study of the gospel and its implications will be helpful in dealing with her.
I have a little more to say, but I have to leave for school. Hope this helps a bit.