Also you might want to check something simple is if the cargo light is on. It wouldn't change the speed of the chime but I know mine does make the chime noise if I take the key out and the cargo light is still on. If she left it on the night before, my truck turns all lights off after so long, so when I get back in and it is still in the on position when I put the key in it will chime to let me know it's still in the on position.

 

i dont think her truck has a cargo light but i could be wrong i know it has a third brake light..... im begining to think that it has to be something to do with the key.....its becoming more and more random i attempted to work on it a few days ago and the damn thing wouldnt make the noise....as soon as she drove it the next day it started doing it again....