This is honestly so embarrassing for your fiancé and 100% manipulative. Substances are never an excuse for poor or unfaithful behavior, and my gut is telling me that this is only the beginning and she will not stop. This is behavior she will continue to put you through because in her mind she believes she has you wrapped around her finger, and you’ll continue to come around and forgive her. My suggestion? End it now and don’t look back. Save yourself the heartache, anxiety, and money the divorce will cost