Facebook messages

Answer is given.

Repeated query.

When messages are sent from one account to another then these messages are not saved in the original account they are saved in the forwarding account. This means that when your wife sends you a message from her Facebook account then that message reaches your account and will stay there despite the fact that she could delete her account and will not affect the messages sent.

You can still verify the messages sent to your account despite the fact that she can delete her account which should not affect the messages sent.