What does my sister hope to gain by breaking off contact and trying to get my closest friend & my mother to work against me? How can my mother forget the past 12 years of care I’ve given / saving her life and replace them with 3 months of this sister? Has / Is my sister poisoning any more of my friendships ? Is there anything else I ought to know?
I did a tarot card reading for you. First , don't react to her behavior. Continue doing things to remind your mother how much she means to you. Lay low for a while and see what happens. Take this time to focus on yourself. What are your goals and take action to accomplish them. After things have settled down, and you may even get more information about this, try to have a calm set down conversation with your sister. Calmly tell her how her actions made you feel ask her if she's ok and let her know you are there.
The Tower card in reverse shows no resolution to this feud anytime soon. I do see you being able to break free of their negativity within the next couple months, (Oct. or Nov). The Page of Swords shows you leaving moving on from the situation. The King of Wands in reverse shows you will not soon forget how they treated you. This moving on will be your choice to save your sanity (Two of Cups). Take care, dear one. People can be toxic, but that doesn't mean you have to live in their toxicity.
I hear you ask, "Will I get justice?" and "Am I so unworthy?" Your situation is purely karmic from past lives. You have no control over this situation. Your mother and sister will reconcile with you. I see a bucket of water. There could be an emotional crisis in their lives when they will reach out to you. Embrace them then. For now, please press the PAUSE button in your mind when their thoughts disturb you. Your mother has clearly not forgotten anything that you have done for her. She's in a state of conflict herself. You will get justice.