I personally would not chose to focus on her OSAS doctrine but instead to give her a more clear understanding of the New Birth experience. If she can get a revelation of
Acts 2:38 then I would say her OSAS persuasion will not be much of an issue.
The Baptists borrow OSAS (or the perseverance of the saints) from Calvinism, while rejecting the other 4 points. If she becomes ardent in defending the OSAS doctrine you might show her its roots. Then, the scriptures against it are irrefutable. One excellent verse is
I Cor. 6:9.