Hi Jonttu01,
I'd like to welcome you to BPDFAMILY. I'm sorry to hear that. I can relate with how distressing that feels when it's a light switch got turned off and we don't recognize a loved one because their behaviors take a 180.
It helps to talk to people that can relate with you and offer you guidance and support. You're not alone, I went through something similar but different of course and ii know that is heartbreaking.
I'd like to set the meds, the behaviors, her parents aside for a second and ask you if you think that she emotionally checked out of the r/s? Does she keep in touch? Do you try to get through to her?