Questions: Girl's Behavior

So my girlfriend recently made a revelation that sort of blew my mind.

I kind of figured that women would wear only underwear under long dresses/skirts, and I was right, I saw my girlfriend getting dressed and that's what she did.

But the weather's gotten hot and the other day I saw her throw on a pretty short and flowy dress that hit only slightly longer than mid-thigh and rode up when sitting over her bra and underwear and then she... just put her shoes on and headed out that way. She didn't put on shorts underneath.

And the whole time I was out with her I kept feeling some second hand embarrassment for her. As if her underwear would be flashed in public in any minute. I kept paying attention to how the wind blew her dress. How it rode up when she sat and crossed her legs. When she climbed up stairs. Thankfully her underwear was never flashed.

When I brought this thing up of why she didn't wear shorts underneath her short dress she literally spit out her water at me and bursted out laughing. About how she never met another woman who does this.

And then I brought up embarrassment or underwear being flashed and she said that as long as you keep your legs together, squat instead of bending over to get something, lightly hold your dress in the wind, etc, no one should ever see your underwear anyway. And that even if anyone saw her underwear she wouldn't care anyway because she wears bikinis at the beach all the time and has bikini pics on her social media.

And honestly mind blown. I'm wondering if most women do what my girlfriend does because I genuinely don't know.