Ok heres one for ya.
Get some empty soda cans Attach them to some 20Lb test line. Tie the other end of the line to the underside of her car.
then take the cans and place them on something under her car so she wont see them as she approaches.
At some point as she drives down the road. The cans will fall off and she will be clang clang clanging dragging them down the road
Option two. Mail her a package with this note. "Dear (insert her name) Had a great time the other night. Thanks! I noticed you left your underwear here when you left. Since I am going out of town I wont have time to stop by and bring them to you. So I thought I'd mail them. Hope to talkto you soon.
Bob"
Inside the package include one pair of womans underwear.. now the size is important here
Send her the LARGEST sized panties you can find.

option 3. You can prank two with one with this one.
Call the floral shop and order her a dozen roses delived to her.
The catch is. You want them delivered with the flowers cut off. Just the stems.
Screw the roses. Give her the thorns.