Is euthanasia ok?

Mrs. Brown has ALS (Lou Gehrig's disease). She is told that she has six months of relative normality before her condition will worsen. After six months, her body will rapidly shut down. She will no longer be able to care for herself, she will no longer be able to move and she will no longer be able to speak and express herself. Her mind will be effectively locked inside her body. Mrs. Brown would like to end her life before her condition gets worse as she doesn't want to live in the vegetive state when the disease takes full affect on her body. She wants to receive euthanasia by a professional medical practitioner to assist in her suicide.