If you have good pictures of your tank, bring them to the aquarium maintenance folks, and get your estimate based on what it would take in euqiptment, setup, livestock, and months of maintenance to restore your tank to the level in the picture. I wouldn't exaggerate, you want to be absolutely belivable.
Have any manual labor that needs doing? My neighbor was robbed by some neighborhood kids (back when I lived in the country), and even after the property was returned he had them raking his lawn and doing his gardening for a whole year. Maybe you'd accept her working for your favorite charity for awhile. If you can't get the money back, you can hang pressing charges over her head to get out what you can.