In a bar. Dogged persistence and a good word from her BFF. I wasn't trying to rob a cradle here, never have been. She was nice, pretty and behaved more mature, like she was in her late teens or early twenties. I was never in doubt about her being on the wrong side of the age of consent, so I didn't feel any need to make sure. I had seen a few that were obviously of questionable age and I steered clear of them. As I said before, I wasn't looking for a youngster. Never had been. That doesn't float my boat.
You must have me confused with someone else. I am not a teacher, never have been and don't want to be either. I didn't feel uncomfortable if that's what you are suggesting. As I said before, she didn't look like 'jail bait'.
I never had a burning desire to find out how old (or young) she was from a legal point of view, but after a few dates, and talking about a mutual friend's birthday party, I casually asked when her birthday was. Dates were exchanged, no big deal. We got married about two years later.
I do recall my Best Man best buddy having a laugh when, on the eve of getting married, I told him I was two months older than my future father-in-law. Her parents didn't care about the age gap either.
But enough about me and back to my original comment about the friend of the OP that you find contradictory. I was going by my 'gut feel'. The way I see it, if the question of age is stirring one's 'gut feel', then it is probably best to err on the side of caution.
Anyway, the OP's friend has checked her ID and the girl is 18. No problem and good luck.