How to connect with my younger sister.

Hey guys, I’m a 18F on my last semester of my last year of high school and I have a younger sister who is 12F. She’s my best friend and I love her very dearly. We have one older sister who ran out on our family within the week she turned 18 (she’s 20 months older than me) and three younger siblings (10F, 7M, 6F) it’s a full house and she’s an over achiever.

Her and I share a room and I spent a lot of time with her (it’s limited of course). Recently, she has been super moody and avoidant. Everyone has noticed this change in her but me especially. She takes her frustration out on me often with eyerolls or brushing past me. She tends to blame me for a lot, either overwhelming her or getting her in trouble. I don’t know how to connect with her anymore, she’s mostly on her phone when we’re upstairs or she’s extremely critical. Her comments and such really don’t bother me since I’m not insecure but I am worried about her and our relationship.

How can I reach her again without seeking parental intervention? Is parental intervention necessary? How should I meet her needs? Questions welcomed in comments regarding situation. Thanks!