She has the Church copy of their marriage license. That worked at the time. She has never had the "official" copy from the courthouse. That's what she'll need now. She got her first drivers license when she was 16 living at home. She's 55. I don't remember needing a birth certificate to get a drivers license in 1986? At least not in MO. 

She has the ability to get everything she needs, sure. But she'll have to take at least a day off work, and pay money to get it. This isn't a "left" thing. This is "The Right, is trying to once again solve a problem that doesn't exist" thing. 

Would you be Ok with getting all new documents, and going into a federal database to buy a firearm?