Chia chair is a good idea.
If you do the fish in the car thing you need two fish. One you put on her drivers seat, the other you hide so they think they got it out but there's still one in there stinking.
Try to get a really big Victoria's secret box and send it to her at the office. Hell write up a fake label and just deliver it yourself so its sitting like right in front of your door. Fill it full of packing peanuts with just a little note at the bottom. Maybe also put something really heavy in it that it takes a couple people to lift so she'll have to secure help with her giant Victoria's secret box.
Get her keyboard over the weekend and wire a switch into it, connected to the space bar, that basically disables the whole thing every time the space bar is pushed.
The best pranks are group ones. Get everyone else in the office to look at her and laugh every time they walk by. When she asks they just shake their head and keep laughing. See how long it takes her to get pissed that she can't figure it out. Or, maybe have everyone walk singly into her office and ask for a copy of something that she has to look up and print out. One gets it, a little while later she has to do it again. Every few times change the item so she doesn't get wise and mass print.
Get some raisin like snacks and leave them on her desk. A couple days later after they've been enjoyed, put a picture on her desktop. Picture shows someone bagging up deer pellets into a like container.
Get a different car key of the same make and switch it on her key ring. Set blowers, wipers and radio all on high. Hopefully she won't detect these as she's so pissed that her key wasn't working. This can be combined with the paper punches in the vent for extra emphasis.
Jack her car up and put it on blocks just high enough that the tires aren't touching the ground.
Fill her office with a colorful selection of hallway plants. This would work well with the chia chair.
Get a remote doorbell and rig it to her seat so every time she sits down it goes off. Hide the chime in a ceiling panel. May have even better results if it sounds like a doorbell she actually has to answer for work reasons.
For best results, combine as many as you can into one whammy! Just when she thinks one is over, another waits around the corner. That should make her tired of pranks and swearing fealty to your supremacy.