How can I prove that I can afford to make my car payment in an upcoming reaffirmation agreement hearing?

I filed for Chapter 7 Bankruptcy in Michigan. The only secured debt that I have is a car loan which I signed a reaffirmation agreement for. Now I have to go to court to prove that I will be able to afford my car payments. My question is how do I prove I can make my payment to the judge? My parents live with me and my mother was my co-signer for the loan. She plans on going and telling the judge that if I can't make my payments she will do it. She doesn't have a very large income though so I am not sure how much of an impact that will have. I really can afford the payments myself but the way they figure expenses for basic things like food and clothing differ from the way I budget. I spend much less than other people apparently. Any suggestions as to how I can prove that the payments will be made would be greatly appreciated. Thank you