Two things are important here in my opinion....
1st - Your brother's mental health. He has probably supressed these feelings and emotions for years and years. It will feel better to open the "windows of the mind" and air out everything. It will feel very liberating. During this process he may discover if this early sexual tryst has hurt his ability to have various relationships. I know that many people have trust issues in relationships when they have been sexualized at an early age by an adult. Sad but true. So of utmost concern is what does he want to do?
2nd - This woman should not be trusted to be around other children. Her new appointment will only allow her greater access to young men and women. She should not be allowed to sexualize any more youngsters. While your brother may have wanted his encounter with her.....ask him if he thinks other 14 year old boys would know whether or not it is appropriate and if they should be sexualized that early by an adult.
Your mother is being a typical Dub.... "maybe Jehoba has forgiven her"? YEAH, WHAT ABOUT THE LAWS OF THE LAND? These sickos thrive on hiding their behaviors...light needs to be shined in their dark corner and exposed for who they are.