Put dog **** under her drivers seat. Every morning she'll say "god my car smells like ****" but they will continue to drive it and never look for the cause of the smell. Trust me it works.
Post it notes are really weak. When I was in college, this girl put an open can of tuna fish behind my buddies radiator, by unscrewing the cover plate off, ingenious. So I covered her windshield with stickers from a pricing gun (remember when stuff at the supermarket had the little price sticker on it?!). The bargain basement price was 69 69, of course!
As I was leaving the grociery store last night around 8:45pm, I witnessed a dude saran wrapping a white Dodge truck. I had to stop my car and laugh. He just smiled and kept wrapping.