What she "thinks" doesn't hold up in court.
Sure it does. Or can. If it passes the three prong test, it's a marriage. It's not at ALL uncommon for the marriage to be "proved up" for the first time in a divorce proceeding. You could easily find yourself having to defend against a marriage claim if there's any chance of all three prongs having EVER been valid. Something as simple as her referring to you as her husband, once, and you not refuting it could help establish such.
https://www.traviscountytx.gov/dro/common-law