No way can you parse or argue your way out of this hole...you were completely and catastrophically wrong with your original post.
Sacajawea is technically correct, albeit in a most likely trivial way.
Should the kid have checked? Yeah. But it’s - as she conceded - not an offense appropriate for calling 911. Though maybe also the line looked obvious but wasn’t.
A more important reason a property owner might object to having their lawn mowed by someone else, is that - as I recall - in Ohio and some other places, if you mow property for 7 years...it’s yours, and becomes the new boundary line.