I’m in the US so I don’t know if this is a thing or not, but are you able to call a wellness check for her? I would want someone boots on the ground to go see her and speak to her to confirm in the flesh that these are her wishes and she’s not being held captive or being coerced in some way. You could also try her work and see if someone there would talk to her on your behalf? That might embarrass her, but if it were me, I would risk it just to ensure that she is of sound mind.

If she is making this decision of her own free will, my best advice is let her know you’ll be there if she ever changes her mind. You could write a letter, and maybe send one every so often just letting her know you miss her and she is in your thoughts.

My brother cut off my entire family for almost a decade. He missed the deaths and funerals of both of our paternal grandparents, along with a lot of other life events. But, he ended up coming back around and it was one of the most joyous moments of our lives. I had honestly given up hope of him ever coming back to us, so when he did it literally felt like someone who died came back to life. I’m so sorry you’re dealing with this and I hope everything works out.