Disrespectful Neighbors

Ok, I know the land behind my garage isn't ours, BUT...it was/is the cause to our garage being pushed over and rotting when we bought the house all because it is a bit of a wasteland where all my neighbors dump their yard wastes back there. When the stuff decomposes it becomes heavy dirt pushing on our freshly renovated garage. I've asked my one neighbor once already to please stop putting her garden waste back there. She got a compost bin and the city picks this stuff up! WHY put it back there?! I noticed she put a bunch of stuff right up against the garage too. Thanks! I am quite annoyed by this and I am not sure what else to do. I know it's her yard waste because it's the same exact plant matter as those in her yard! I have picked up some of the stuff and thrown it back into her yard. I don't know if she'll get the picture because I've done that before and she still didn't. Next time maybe I'll bag the stuff and leave it in her yard with a note on it "The city picks this stuff up. Much appreciated if you would make use of our tax dollars instead." Think she would get it?