I love my sister and family so much I just want everyone to be happy

[worried_sister]

Hi,
Please help me. My little sister has been diagnosed with BPD. I'm in college and usually live on campus but I'm living at home this year cause of covid. I just want things to be okay. My parents have been treating me like a third parent in trying to manage my sister. My mom asks me really heavy questions on how to parent my sister and I don't know how to tell her that I need more boundaries. I want to be there for my whole family but it's gotten to the point of me losing sleep because I need to help navigate fights and other difficult situations involving my sister at night. I love her so much, all I want is for her to be happy. It's so hard to sympathize with her when she's yelling at me, for example, about how I took too long making waffles (she was mad because she thought I cared more about making waffles than hanging out with her). When she was little she used to have everyone apologize to her all the time and then things would be okay, but now, it seems like nothing gets her out of her anger except time. Basically, I have two questions: How do I talk to my parents about not putting me in a parental role, and how do I act with my sister in the moment when she's yelling at me over something that to her seems like a big deal, but to me feels like an overreaction? I would never tell her that I think it's an overreaction, because I know that's invalidating. I mean, how do I navigate these situations in the moment while still respecting her point of view? I love her so much. Please help me.