who you believe did something very upsetting to you in order to restore peace in your family? This family member hurt me and I used to be very close to them. I do believe they are wrong and made it worst by the way they handled things. But my parents are getting older and my mother is saddened by it all. I also have a nephew who is fighting cancer and my brother would like solidarity. This rift has spread to another sister who is not speaking to this person either. Probably if I repaired it she would to and I guess everybody would be happy.
If this is the situation, yes I would make the peace. I can understand you not wanting your ds to go to work for her, but he is an adult and bears the responsibility for making the decision to do it, and the decision to continue working for her. This isn't all your sister's fault.