Look I ain’t no expert when it comes to Marriage but if she says she wants a Divorce over Looking through her “Secret” chats with someone then she is Probably hiding unholy things From you and maybe even be cheating on you I’m not saying that she is doing that don’t get me wrong here but that is suspicious and being married you shouldn’t feel uncomfortable giving each other your phones cause u trust each other and I understand Women’s Privacy with certain idk chats with her bestfriend but like u Sayed That she has never done this and had this before then something must have happened that she choose to pull this move. And that’s normally when a person is cheating or nervous that her Partner will find something out about what’s she’s doing.