I (18F) have a sister (14F) who I love a lot, but I don’t know how to help her. She thinks I’m always mad at her or that I hate her.
She’s very sensitive to tone, so she assumed that if something isn’t said in the way she wants, that they want her to leave and DESPISE her.
She also tends to think if you don’t absolutely approve of her and love everything she does, that you hate her. She has tried sabotaging many friendships under the belief that they hate her and want to abandon her. She goes from thinking they’re wonderful to thinking they’re terrible people very quickly.
You're describing NPD or maybe BPD... Maybe have a read about those on Wikipedia or such.
Whether your sister's behaviour is extreme enough to be diagnoseable or not, the strategies and guidance on living with, and being in a relationship with, people who behave that way would be of value to you.
From what you've said here, I'm leaning towards believing your sister genuinely believes what these strong feelings are telling her. If so, it means you can't explain or logic her back to the truth sadly. Anything you say will be distorted to fit with her negative beliefs 😟
You're right that this might look like BPD, but that's also a huge conclusion to draw from only a couple sentences. It's extremely rare to diagnose BPD before age 18 because it has too much overlap with just... the nature of moody teens and puberty.
OP, it might be useful to research BPD but moreso than anything, just give her time and make sure she knows you're there if she needs you. Give her reassurance and try asking her about why she thinks people hate her, and maybe try working through it with her (try bringing logic into it, but try to get her to come up with the logic rather than telling her directly).
I totally agree. Diagnosis isn't possible for anyone currently involved in this thread, I'm suggesting understanding those conditions might give OP some of the answers they're asking for, regardless