If you go into the account settings (there is a drop down arrow beside your account name and "home" in the upper right corner) you open a page for all of that. You can set mail preferences by looking in the upper left side of the account page for NOTIFICATIONS.

On the notifications page scroll down to the "All Notifications" group and click the Facebook line to open the larger menu. I have unchecked most of the items there. I think you'll need to uncheck "sends you a message" or any of the other things she is doing. I she suggesting friends, tagging, etc? Then uncheck those.

SRS