I tutored some very angry at-risk high school kids for several years. The single most valuable thing I was able to do for them was to listen to their issues and feelings supportively, compassionately, and without judgement. Amazingly, once these kids had been heard by an adult, they were able and willing jump through academic hoops that had seemed hopeless or pointless to them before then. Those kids loved me, and I fell in love with them. It was one of my most rewarding jobs ever.
But it's so much easier on a child's life if that kind of support starts earlier than high school. It sounds as though you might be an important stepping stone toward this little boy's healing.
The wonderful and wise book How to Talk So Kids Will Listen, and Listen So Kids Will Talk, by Faber and Mazlish, is a parenting workshop between covers. It's divided into easy-to-read and easy-to-digest chapters, with easy-to-try hands-on exercises, and lots of coaching and encouragement. I can't think of a better resource for any young parent.
Especially a mom who's dealing with emotional trauma in a child. One of the great strengths of this book is that it acknowledges that we all have needs, both parent and child, and that for a family to run smoothly, those needs must be recognized and addressed. There are practical, real-life examples throughout on how to do this.
This little book is a wonderful addition to any parenting library – if you think this mom won't read or can't afford it, perhaps you could get a copy for yourself and coach her through some of her son's difficult behaviors. He won't, of course, "get over" his feelings, but he can be taught to understand and handle them better, and that will most effectively start with you, his mom, and other caretakers understanding that his needs are legitimate.