UPS/Landlord problem...What do I do?

Are you positive it was your landlord?

The main offender was UPS. It is their job to deliver your package to you and not some random person they deem to be your signature substitute. I'd definitely file a complaint with your UPS.
 
Maybe you should ship yourself a package. A box with a dead fish in it, then put a note on the top of it. "A gift from me to you. STOP OPENING MY PACKAGES!!" Think she'll get the hint?