First of all, retro isn’t some euphemism for granny panties. Yeah, it’s high-waisted and pretty much covers all of her ass, but don’t underestimate it’s boner-inducing powers. (If the woman to the left sauntered into your bedroom, would you really be bummed out?)
According to Baumgartner, this style of underwear is designed to exaggerate the female figure, so when a woman wears this she wants you to be mesmerized by her curves. “She’s the type of woman who feels powerful in her femininity — but she still wants you to make the first move.” Translation: She may want to start out in missionary, but there’s no telling where she’ll want to end up.