No pullups for this girl!!

Well, after a week off with my little lovelies and Mandy bound and determined to go potty despite my laziness, any time she wears a pull up she pees in it! But if she has on a diaper or panties......NO pee pee! I just don't get this kid. I know they are all different but WOW. Today she has had no accidents and went poo poo in the potty! I don't get it, she is definitely a girl who knows when and what she wants not to mention how to get it! I am guessing having a brother who will cheer for you every time you sit on the potty and demand that you both get stickers doesn't hurt. :)