Do I have a reason to be upset with his mom for giving him a car?

My sons father owes me $5000+ in back childsupport. He also owes me $5000+ for a car I co-signed that he quit paying for and I was forced to pay the monthly payments on.His payments were 377 and is child support is 429. His mother was willing to pay off his debt to me for the $5000 in exchange for the car back and insisted he would make the payments on it as well. I was reluctant to give him the car back since he couldnt pay child support how could he pay car payments? Plus why was she not more concerned about paying child support debt then the car debt when it was for the benefit of her grandson. Now his mom is going to give him a car that she owns, free of charge with no payments. This guarantees I will never see the money for the car now, he has no encentive to pay it. Do I have a reason to be upset with her? Do you think that she is slapping me in the face by rewarding his wrongdoings? What should I say to her?