I thought the coda was fine. It showed, and the elder actress made you feel, how Mattie had stayed her resolute, unyielding self for 25 years and had paid a cost for it. My first impression on seeing the actress was that she looked older than 14+25 years, but then I realized, of course she does--it's been a hard existence she's led for herself.
I like the original movie fine, but a comparison with the hokey uplift at its ending--"Come see a fat old man sometime!"--really exemplifies why this one is vastly better.