You do need to do an accounting of her deposit. Make out the disposition sheet showing what you are subtracting. You can deduct for unpaid rent, damages/repairs to the unit, rent up to the day the unit is re-rented, the difference in the rent amounts if you have to rent it for less money, the costs of advertising the unit, any unpaid utilities that you end up being responsible for (usually the water or heat bill can be charged back to the owner if the tenant fails to pay it), agent fees if you use one to find a new tenant, etc. Total these costs up, attach copies of the receipts (if over $125 in CA), subtract it from her deposit, and send the check to her. Be sure to get a signed lease from the new tenant and at least the first month's rent and deposit before you send the statement back. And be sure you send it back to her within the state's time limit.