Oh the 1 in 6 number was totally made up, and was anchored by thinking about randomization which made me think about dice which made me think about 10 sided dice (because I'm a gamer and that's what comes first time mind), which made me think about "1 in 100" chances as compared to "1 in 10" chances, and the latter seemed like a reasonable upper bound on how often you shoud compliment a girl on her looks (based on intuition), and then in case 1 in 10 was still too high I went up to the next most recognizeable dice-size, which was 1-6.

I'm NOT a perfect agent with infinite time, and I haven't thought about this particular instance of this problem before today. But I suspect the upper bound for how often girls need complimenting on their looks from strangers is somewhere in that order of magnitude. I don't think that there's much useful ground between using your intuition and doing a bunch of intensive research.

I could see the answer ranging from 1 in 20 to 1 in 6ish (I'm trying to imagine 1/5 as a viable answer and failing, but at this point I'm hopelessly anchored). That's in the world where everyone in society is trying to do this at once, as opposed to a minority of agents operating against huge cultural biases.