Pants like you've drawn on Wondy here won't stay like that. The gusset will shift about and expose her labia. The only way it won't is if it's pulled really really tightly and then you'll probably see her labia anyway, and quite possibly it will cause a serious chafing injury.
Please, draw underwear sensibly, even if it's outerwear.
Also, those poses are candidates for Escher Girls.