What an interesting question to focus on such a minor character! Charley's mother is very interesting, for sure. I will give you more than five sentences here, but you can pick and choose which ones to glean from for your assignment.
Charley's mother is desperate: her husband is dead and she needs someone to provide for the family. She originally supports Charley's joining the war.
Charley's mother is regretful: because of the previous response, Charley's mother immediately regrets her decision both to allow Charley to go to war and even to see him off. The provider for her family is gone. Further, Charley's mother regrets her decision because she fears her son's disillusionment and death. Even in training, the former is realized:
Training must work, he thought. I'm doing all this without meaning to do it. He felt like a stranger to himself, like another person watching.
Charley's mother is persistent: she repeatedly asks Charley to desert his unit and leave the war effort in order to come back and help the family.
Charley's mother is hopeful: even though she is the one who allows Charley to go off to war, she is also the one who hopes avidly for her son to return home. (She needs help with the farm and also loves her son.)
Therefore, as a minor character, Charley's mother is especially interesting in regards to the family dynamic and also as an escape from the war-torn landscape.