get one of those live traps and catch it and keep it for a couple days then go knock on her door and say now lady if dont leave me alone the next time i will hall it off to the pound far away from here.
Don't threaten to hurt it or any thing just let it free. I'm sure she will leave you alone.
If she does not then get some skunk wee and one of those meat injectors poke it trough the door seal of her car and let it have it , If she says any thing about it just say it smells like cas wiss to me..
She will have to sell the car because the stuff will not come out and every time it gets hot out side it will just reek like mad. You can get the stuff on the net some people use it for trap lure god that stuff is nasty and stinky too.
Or you can trap the cat and put the skunk sent on the cat I'm sure she will injoy the new sent of her cat..