Talk with the sister...
... There are a few people in my life that are becoming very supportive about mine and O's blossoming relationship when they were not so before.
One of them is my sister - conservative in her own right.
She called me today, and was talking about guys she is/ had dated, and how she hates the feeling of jealousy she has towards them dating or spending time with someone else (after they broke up or stopped dating - she is not poly). I got the chance to talk to her about jealousy and how it can be looked at as a symptom of another problem, like insecurity.
It was wonderful talking to her about this! I love knowing that the small steps I make in my life can be helpful to those I love! I feel that this new insight might just help her in many aspects of her life.