unauthorized use of credit card

[454help]

My soon to be ex-wife used my credit card to make an unauthorized charge to pay for an attorney. Credit card co. said transaction was made without the card present. I had signed a paper from her attorney saying that I am not liable for this charge if i do not reverse the charges. I called the credit card co. and they told me if she defaults on payment i am still liable. My question is can a still reverse charges and have her prosecuted for fradulant use of a credit card even though i said i wouldn't?