On slightly less than lethal solutions your at a slight disadvantage, mostly becuase of proximity. It sounds like you know quite a bit about the yapper so maybe its time to take notes on what she HATES, and then begin implementing them in subtle ways.
A nasty little trick favoured by evil admins everywhere, it to go into the contacts list in Outlook and change a lot of those addresses to a company wide spam by hiding the destination behind what the initial title says. Nothing like a company wide email full of personal details for true humiliation...
Change the biro inks to different colours, this will make baby jesus cry if you do it often enough.
Coat the monitor in a light smear of vasoline, just enough so its good and blurry. This is damn near impossible to scrub clean and will cause unessary eye strain and pain.
Hide a sardine in the mouthpiece of the phone, he'll fester there nicely over a weekend if you put him in there on friday arvo. The trick to sardine infestation is not to use a lot of sardine, just a small chunk.
Dust the mouseball in graphite grease, possibly the most evil substance to get out of everything, including skin.
If she takes off her shoes, throw in a bit of Iron oxide powder in there, brickies use it in cement. The nice thing about this is that it eventually creeps up over the skin through the day and gives it a nice shade of crappy orange-red.
Of course, how you do this is up to you.