SM has been in my life 20 years and it's always been rigid. 2 years ago on Mother's Day, my dad served her divorce papers and I had texted her saying "I appreciate you thanks for all you do" etc not knowing she'd been served.

She went off on me on how my dad was leaving her, she wanted a $50K kitchen remodel, how my dad gives everyone money but her (not true) and was shitting on my husband, too. At the time, my stepsis had a loser boyfriend living with them so she projected a lot of hate onto my husband. Days later, she texted me asking how much money my dad gave me for a birthday gift!

I saw red and texted her every thought on my mind. From every one we know calling her a golddigger to how I have never seen her genuinely happy because she is so fake/ narcissistic. One of her cousins told me she is most likely undiagnosed bipolar (runs heavily in their family.)

Originally, she wasn't going to attend my cousin's wedding in Texas this weekend but now she is. I had a dream last night that she insulted me right away and we got into a fight but I was hitting her with no power.

The biggest reason I cut her off was that after having 2 kids of my own and always feeling targeted and abused by her, she will have no control or access to my life to hurt or upset us. My dad even told me she doesn't hate me but she definitely doesn't "love me." Especially as much as her own daughter, my stepsis.

I already told my dad we will spend like 4 hours max at the event and there should be zero chance that we are alone with her. I told dad I will tolerate her but the first negative criticism against me or my family will be met with a swift no contact with her FOREVER. 

Neither my husband nor I trust her but it also hurts my dad by having to travel alone and see his grandkids without her. I really don't think she'll be "mean" to my kids but why should she even have the privilege of being "Grammy" when she clearly loves creating issues where there are none with me?

ETA: when I moved out at 18 11 years ago because I couldn't stand to be around her anymore, she told me that I'd be begging to come back because I never make it on my own. I never looked back and she hates that. She is also convinced that my dad pays our bills because her own daughter can't take care of herself. My dad said that because my step sister can't take care of herself, SM is convinced that I can't either. 

When we found out I was pregnant the first time, totally planned, she did nothing but shit on how I don't have child care or health insurance. That was also false. A close friend of hers also told me that when we planned our second child, she went completely ballistic acting like it was basically my dad's child financially. Anything that she doesn't get directly she is jealous of because she thinks it's going to somebody else. Yes, she is the definition of a golddigger.