Well the character has a broken neck and can't breath without a respirator. She is, however, completely lucid. Essentially her injury is the same as Christopher Reeve's. Prior to the assisted suicide she expresses a desire to end her life and later attempts suicide (twice) on her own. Both times she is revived by the hospital staff.
I guess what I'm asking is does the Catholic Church view the use of a respirator by someone with a high neck break as "burdensome, dangerous, extraordinary, or disproportionate to the expected outcome", to quote the Catechism, if the person with the injury has expressed a desire to accept death without the intervention. Clearly, Catevhism papa. 2278 contemplates the patient making these decisions on his or her own (with spiritual guidance from the Church).
Though not 100% sure, I believe the use of a respirator in such circumstances would still be seen as extraordinary. Others with a better understanding are welcome to correct me if I am wrong. That being said, such a condition would still not justify ending the life by an injection of drugs/poison.