You may not have a choice if she wants a divorce. She's unhappy. You say you won't give up that easily? You say there may be a spiritual component? I think she lost her her mother, she's never fully accepted and a husband in her face constantly questioning and critiquing her actions, she hasn't had time to grieve.
She needs to be away from you awhile, to get her thoughts together and find out if there is anything to save. Losing a parent takes a person a long time to heal.