Long story short, my sister is extremely jealous of me and fluctuates between occasionally being pleasant, and the rest of the time barely tolerating me. Whenever she's around (family occasions etc) it really gets me down because she just gives me the cold shoulder and sends out the vibe that she doesn't like me. This makes me feel ill at ease and like I can't relax and be myself because it will trigger her jealousy and resentment. She takes the slightest opportunity to go nuclear at me, always presenting herself as the victim, and sends texts make me feel like shit basically implying that I'm a terrible person. I spoke to her a bit impatiently at an event this weekend (which I shouldn't have done but it was definitely minor), and she sent me a text saying that I'd spoken to her with hatred, contempt and disgust. It was literally just me being momentarily grumpy.
Is there any way at all that I can put boundaries in place without causing more drama? She doesn't do the texting thing as much anymore because I walk on eggshells around her, but it's always there under the surface. On one previous occasion she threatened to use 'the fullest extent of the law and social services' to be able to see her nephew, my son, purely because she hadn't spoken to me for months and then out of the blue expected me to drop my son off at our parents' so she could see him, which I didn't do (nor did I say she couldn't see him in general however, and the thought hadn't actually crossed my mind.)
I'm actually wondering if sending a message saying that I will consider any further contact of this type as harrassment, because I don't want to deal with it anymore, it's so stressful and horrible getting messages like this and sends me into a spin emotionally. It's not nice feeling like no matter what I do my sister basically can't stand me, especially when she positions herself as the victim in such an extreme way that I start to question everything about myself.