I think that emphasis should be on the scriptures that Kim Davis holds up to be her authority rather than what she did before her conversion.
Simply ask her if she's willing to give a rapist who's forced to wed his victim a marriage license . When she answers no, if she answers at all, then quote Deuteronomy 22:28-29 which says:
"28 If a man happens to meet a virgin who is not pledged to be married and rapes her and they are discovered, 29 he shall pay her father fifty shekels of silver. He must marry the young woman, for he has violated her. He can never divorce her as long as he lives." - Deuteronomy 22:28-29 New International Version
When she gives her excuse for not applying that scripture accuse her of being a hypocrite who wants to pick and choose whatever scripture she feel's like applying.