First, for any 10U pitcher to be able to throw a "waste pitch," she would have to have uncommon control. There is noting wrong with your dd learning the concept. It is carrying out that concept that is the problem. Perhaps, she is being told that when the count is 0-2, throw a ball in the river to let the hitter chase or maybe she is being told to throw a ball up. Both are sound suggestions IF SHE HAS THAT KIND OF CONTROL. Still, for the majority of 10U pitchers. my recommendation is throw your best pitch in those situations.
I forgot to add that pitchers throw waste pitches all of the time in college.