Try and think hypothetically for a moment. If you and BM or SM did not know each other or meet each other through DH...and of course didn't have the kids, and all the drama, bitterness and circumstances that usually make these two women despise each other... Do you think she is someone you could be friends with? Think about how you met your actual best friend or good friend that's in your life now. Just for a moment, replace her with BM or SM. Would there be a connection? Would you click? Is there anything in common? Or would you run for the hills?