How do I get my mom to seek psychological help (Long - please read)

My mom was born to a trashy 14 year old who gave her up for adoption at 4 months old. She was taken in by an older couple who had 3 other kids. Her adoptive parents were cold and distant and her father was verbally and physically abusive throughout her life. Her adopted sister committed suicide about 10 years ago, and my mom was blamed for her death (which she has never let go, even though it is the farthest from the truth). Her adoptive parents “disowned” her after her sisters death. She then found her birth mother who refused to have anything to do with her. My mom has a severe anxiety problem, depression, claustrophobia, no sense of self-worth and difficulty trusting people. She is on medication but she does not take it regularly and when she does, she takes too much. I am no psychiatrist but I suspect there is also an underlying personality disorder. She is very quick to anger when you point out any flaw, she will just not hear it. My fiance and I have talked with her countless times and tried to get her to see a psychiatrist but she refuses. When my dad brings it up with her she calls him a dickhead. My brother stays quiet. My sister doesn’t know what to do. I need to know how to get her into a psychologist. She has deteriorated over the past few years and I am not going to sit back and watch her kill herself because that is my fear. How can I get her into therapy? I live in Toronto, Canada. If anyone can give me ANY information it would be greatly appreciated.