Good morning and happy new year @NajibCoutya,
I am sorry to see that your Wife's emails have disappeared.
If she isn't using our official BT Email app, can you ask her to check her iphone mail app's settings. Go to Settings > Mail, then turn Ask Before Deleting on. If the delete was triggered by the Mail app this may help prevent it in future.
I'm going to send you a private message with some details that we need.
Thanks
DanielS