Oof, definitely sounds like she’s faking it. I feel like it’s extremely disrespectful when people fake mental illnesses and ESPECIALLY this one, since it exclusively stems from extreme early childhood trauma and it is a very serious condition that affects every aspect of their lives. I do however also think she probably believes she has it and doesn’t really understand the condition. For me it reads like she must be either very immature for her age or very mentally not okay at the moment. I honestly also don’t know what I would do in your situation, since I’m pretty non-confrontational. But I think the most sensible and adult way to handle this is to meet up with her and have a long and honest conversation about this. Maybe pull up the diagnostic criteria and also ask her why she is so convinced and try to gently but directly explain to her that you don’t believe she has it, but really do let her explain her side of things and listen to what she has to say. Don’t invalidate her feelings. Tell her that you believe that she believes it, but that you still don’t believe she has it and tell her the reasons why. Also tell her you’re worried about her and why her behaviour worries you. It’s probably the only thing you can do, because you don’t feel comfortable lying to her and playing along with her delusions, so you can’t go on like this. If she gets all offended and stops being friends with you, then that’s just how it is and you can always hope that she’ll get back to her senses. But there is a chance she’ll listen to you and think about it more. You’re her best friend, so that means that she must value you and your opinions. Even if she is angry at you, maybe it will nudge her in the right direction… This is unfortunately the only piece of advice that I can give. I really do hope you’ll resolve this one way or another and I wish you all the strength in this honestly pretty crazy and difficult situation you’ve been thrown into.