It's kind of impossible since she rejects all sunni books of hadith, why don't you try giving her dawah, there's lots of filth in shiaism why don't you point it out to her. For example
1. They allow mutta marriage (temporary marriage) marriages, a man goes to a women and says "I want to marry you for a period of 5 days and that's it, so they get married fulfill their desires and divorce after 5 days". she may as well be a prositute.
2. They accuse the prophet's wife Ayesha of committing adultry, and the worst thing is Allah actually revealed verses of Qur'an clearing her of the accusations. But they still accuse her of adultry to this day.
3. Some believe that the present Qur'an is incomplete and when their mehdi comes he will bring the parts of the Qur'an that are missing. They believe when the prophet pbuh died his companions hid the real Qur'an.
4. They curse the sahabba, they say when their mehdi comes he's going to resurect abu bakr, umar, uthman and then hang them aswell as whip them.
5. They commit shirk by saying that their 12 imams occupy a rank and status higher than the prophets and messengers. And by saying their 12 imams know everything and nothing takes place without the knowledge of their imams.
look at these links about disgusting shiaism.
http://www.*******.com/watch?v=Yrt4BMrH920