It is indeed a toxic "religion". Turns decent, kind human beings into delusional, paranoid, guilt trippers. Im sorry to hear of the passing of your fiancee. Its sad that your mother reacted that way.
My mother tells people im dead, i found the best thing to do was to write her a letter cutting her off from my family. I've felt a lot better since doing this. It's taken away the power she believed she had on me by her shunning me.
Im not gonna tell you what to do, but none of us need toxic people or things in our lives.