No there isn't. Of course her friend can contact you. @Mike-And-Lynne0
As you know it's against Airbnb's T&C to accept third party bookings so you can't consider a booking through the friend. Or you can but it would be highly foolish to do this for a one month booking and if something goes wrong you aren't covered by the Airbnb guarantee.
If you take one month bookings, tell the person who is inquiring you are happy for her friend to contact you and then you can consider her booking.