I’m so sorry about my friend.
Yes, it is the hardest, yet also the easiest decision to make. Dh had to make it for his father. Alvin had made it clear to all of us that he did not want kept alive on life support when his time came. Yet my dmil could not do it, the youngest sil fought us on doing it. Finally dh had the doctor speak bluntly to the whole family about dfil’s chances of recovery. His kidneys and most of his other functions had already shut down. He had not regained consciousness in several days. Then in front of the entire family dh told the doctor what my dfil had told all of us at one time or another. Then said he felt we should honor his father’s wishes. Dmil said yes, but would not sign the papers, she simply could not do it—the hardest decision of her life.
So dh as the oldest child did, the easiest, because he had promised his father he would and he knew that was what Alvin wanted. My dbil second the signature. And we were all with him as he peacefully passed. It was what he wanted. I don’t know if you believe in spirits or not, but dfil showed up two days later looking for dmil to say good-bye and he smiled at me and nodded as I told him where she was. Dh saw him again months later, happily watching us play cards with dmil.
Your friend will leave peacefully, and she will be happy and that is what is important.