You, sir, have a neighbor with a bad case of sour grapes. Quite frankly, it is every pondmeister's nightmare. No pond owner wants to suffer any level of control of valuable drainage. It is also a classic example to all newbies looking for potential pondsites; make sure nobody can cut you off....or at least, be as sure as possible.
-
I wonder if she might have a glimmer of a case for your direct effect on her "pre-existing" water feature...???