I don't know, maybe I'm weird, but I think it's pretty damn bold of this co-worker to do what she did. I wouldn't have let her borrow my car in the first place, especially if there was a company car she could have used instead. That said, I know I sure as hell wouldn't be okay with someone cutting off all communication with me once they had the keys to my car, accident or not.

Hopefully she managed to get in touch with the lady one way or another. And hopefully she'll learn to stop being such a doormat, bless her heart.