His marriages really were disastrous, and his second wife really did say that. She (and he) even really might have felt that way, despite the immense problems in their relationship.

Just to give you a sense of the problems in their famous relationship, Dostoevsky was once lost all of her belongings while gambling.

If you're interested further, Joseph Frank's five volume biography of Dostoevsky is a masterpiece in itself, and would give you a sense of how difficult, but also how strongly emotional their relationship was.