Shame, I can only imagine what a terrible weekend it must have been for you and how hurt you were.
I don't have any advice on how to further encourage your mother to seek help. Maybe if she carries on voicing her suicidal intentions, your father (Or anyone for that matter) can forcefully take her to a hospital for her own safety, where she will be offered treatment?
Just remember that this is not your mother talking to you in a hurtful manner - it is her undiagnosed illness. As hard as it may be, you cann cannot take offence to what she says; I truely don't believe she means it like that - she is simply ill and really needs help