After much practice I've figured out how to pee standing, without making a mess.
First the girl must open her legs and bend her knees a little while pushing her pussy forward. With long pants or tight shorts she has to drop them some, but with lose shorts she can then with one hand hold them aside while with the other hand, using two fingers, hold her pussy lips open so that they will not interfear with the stream as it shoots out of her pee hole which is now clear of lips and exposed. Once at that point it just takes some practice moving both her pelvis and fingers to aim her stream.
One other thing. As she feels her bladder nearing empty and her stream about to stop she must then give a push to empty the last remaining bit or it will drip and run down her legs.