Joint Tax refund

I recently filed a married joint Tax return with my spouse who I am currently separated from. I only worked for the first two months of 2015 and the rest was temporary disability/ permanent disability. She worked all year. Through text we agreed to divide the money as she gets her portion and I get mine and we split whatever we get for my son. Before signing the return I spoke to the accountant and he explained that since I paid all of the household expenses and all health insurance premiums, that we should split everything in half. My spouse agreed to it over the phone with the accountant and my mother in the room. When the check came in the mail. She texted me and said that we will go the next day to cash the check since it had both our names on it. The next day comes and I come to find out that she deposited the check through atm without my signature. The bank accepted it and she gave me a check for my portion not the half that we agreed on over the phone. I'm just wondering if there is anything I can do as to her cashing a check with both our names on it into her account? Is it even worth the process for $600? What should I do with the check that she gave me? Thanks. Also I'm in NJ.