Hi, I am on the lookout for a strappy summer nightdress, preferably cotton or cotton mix, that is not so short that it rides up and my bum is always sticking out! I am short myself (5 foot 3), but nevertheless they all do this. I don't want a "long" one that looks like an old lady "nightgown", just one that covers my bum when I am lying down. I am hunting in vain! Has anyone any suggestions?