I think the joke is that her mom thought her face wasn't suitably stoic enough, while Maho meant her legs were open.
Really...? I thought it was because she thought her eyes were way too open? XD Anyways, notice how furrowed she keeps her eyes in almost every image. It's sort of become a thing with her. In fact, I sometimes wonder if half-closed eyes would be wasted on her? :D
Maybe it's a regional cultural thing, but in my book the leg thing doesn't matter if she's wearing pants. With pants on, there's not really much to see there anyways.
