Legally though - she gets to self direct. I don't have power to overide her and force her to accept any care. She doesn't have dementia- and is quite sharp mentally. Emotionally, the BPD has an effect but still she passes mental competency tests. The medical POA is on record if they need it. I could step in if she wasn't able to decide for herself.
Yeah, it's more of a BPD thing than an age thing- we've learned that with my young adult BPD daughter. Her whole life, the doctor would say, "This is a typical case and it's clearing up nicely...." She hears, "You almost died and you're so very brave, so strong to withstand this on your own." We'd just roll our eyes and laugh.
Meanwhile, If the doctor said to do x, y, and z, my kid would focus in on what she wanted and shout it from the rooftops...I can't be responsible because of x! The doctor said so! But she'd refuse y and z for whatever reason and try to re-write what the doctor said in the first place.
It's definitely maddening but I found it easier to laugh and let it go. It's on her and if she wants to get sicker because she knows better, then so be it. I will not stand in her way.