She's dead meat.
Go to www.cia.gov and the CSI-homepage to read the latest on forensic techniques. Then kill her accordingly.
Maybe you can use that clear bra 3M coating?
You can always keep a picture of her for sentimental reasons.
But you gotta kill her.

Throwing her out just aint enough.
God knows what other poor sod she might end up with and end up scratching HIS car. Somebody has to stop her serial-scratching reign of terror!
Should you get caught, I'm sure most judge will be lenient..if it's a male judge.He'll understand, and probably give her a posthumous sentence.

If all this killing and scratch-repairing just stresses you up, remember the old saying: "Kill, relax. Kill, relax".

If you opt to worm out of doing the right thing and decide to keep her, you must take pics of her as she licks the paint back to pristine condition.
It might take a year, but it beats waking up in a plastic bag in a bottomless lake and finding out you're pretty dead.
Just a thought.