naccs, I"m sorry to hear about the damage to your sink. I'm afraid that you'll spend more time, money and emotional energy trying to pursue this young woman in court. She clearly has no interest in making things right.
A damage insurance waiver is probably the best course of action for all your future rentals. I personally don't like the term "damage waiver" because it may give guests the impression that they can do whatever they want because any damages are now "waived". Still, it's better than no protection at all. Good luck!
I agree with AmyG - it looks like you'll have to absorb this one. Hopefully her rent payment was at least enough to cover the damage so you don't take a loss.
Our policy is to ALWAYS require either a pre-authorization on their credit card, or an actual charge on their card (refunded after they check out with a clean bill of health for the house) for $500. That's enough to fix a hole in the wall or cover the majority of a new TV.
In most cases we avoid renting to groups that are all same-sex (ladies can be as bad as the guys), but if we're borderline on it and decide to rent, we require them to get the HomeAway CSA $3000 damage insurance policy ($50). This is in ADDITION to the $500 damage deposit. The insurance would have covered the sink for you, but it doesn't cover things like smoking in the house or leaving it in a really messy shape.
I had to take three tenants , all on one lease, to two different small claims courts. I sues each one in the district they live. It took many months but I won the $3000 in damages they did. The proof was in the pictures. Pictures before and pictures after their rental.
Yes it takes time and effort, but do you really want these people to get away with this and to do it to some one else next time.