as far as fucking up the mustang goes:
1) freeze about 6 cans of cheap ass shaving cream overnight
2) saw the cans in half with a simple hack saw or hand saw
3) around 2am when it's safe and she wont be in the whip for a while, get in that mfkr and place the half cans under her seats, in the glove box, under the accelerator
and when she wakes up the next morning ever cubic centimeter of room in her interior will be replaced by shaving cream. And it's not like you vandalized the shit so you can't go to jail for it, she just needs to spend a lot of time cleaning it.
1) freeze about 6 cans of cheap ass shaving cream overnight
2) saw the cans in half with a simple hack saw or hand saw
3) around 2am when it's safe and she wont be in the whip for a while, get in that mfkr and place the half cans under her seats, in the glove box, under the accelerator
and when she wakes up the next morning ever cubic centimeter of room in her interior will be replaced by shaving cream. And it's not like you vandalized the shit so you can't go to jail for it, she just needs to spend a lot of time cleaning it.
That won't do anything but ooze out of the can. It will expand a bit, but it won't fill up her car.