Am I responsible for part of her deductible even though her property was damaged too?

As far as I can recall, Hurricane Sandy did not affect Nevada, the state I am practicing in. So, you need to talk to a local attorney.

This is an odd situation. If she had no insurance, she would not be responsible for the damage to your mattress and you could not sue her for it. Since she had insurance, it covers her loss, and I suppose the losses of property to others that was on the premises. You say that her insurance reimbursed you for your loss, so I assume the check was written directly to you. In that case, I do not think you have a legal obligation to pay part of the deductable. You may fell a moral obligation. If she included your mattress in her claim, and she is offering to pay you out of what she received, the legal obligations are more muddled. She may be under no obligation to pay you anything because it is her claim (however, she may be guilty of insurance fraud for including your property in her claim). Regardless of who the check went to, if you both want to be fair, you could pro-rate the deductable. If her deductable was $1000.00, and She received #0,000.00 and you received $1000.00, you pay her 1,000/30000 x 1000 = $33.33. I made those figures up, but the formula is the amount received for the mattress divided by the total amount received times the deductable.

As a good faith gesture, pro-rate the deductible based upon the % of loss that you incurred as compared to the total loss. Was she charging you for the storage.

Not legally, but it would be a nice thing to do to offer to pay part of the deductible.

Attorneys can only offer legal advice for cases involving States in which they are licensed to practice or they would be committing the unauthorized practice of law. I am not licensed in any State that was directly impacted by Hurricane Sandy so I cannot provide you any legal advice. You should re-ask your Question and select whatever State the mattress was located in when it was damaged.