This has to be one of the weakest arguments I’ve ever seen. Hillary Clinton may be Bill Clinton’s wife, but she has never been elected to the office herself, despite the “common law.” Using this argument we have always had two people elected President as long as the President was married. This is a ridiculous argument.
It was also a custom to only run for two terms, but it was not a “Constitutional” custom as this was not in the Constitution.
The marriage argument is incorrect but the conclusion is correct. She cannot serve (at least more than one term, I’d have to review her authority in 1997-2001).
Read the amendment sometime. It is really short and most of the language is just about who is or isn’t covered by it at the time of its passing.