Photoshop Elements :: Create Smart Search With Pictures From Only One Person (saved Search)

I have many pictures (about 10'000). Now i need a search (smart search) with pictures where only my mother (is marked)
 
On all my pictures each person is tagged. For my mother the Person Tag is called "mother"
 
I created a saved search with the criteria Person include "mother". The problem now is that also pictures are shown with my mother and other persons. But i would like only pictures from my mother without other persons. Something like... "Person is mother and not person "sister" and not person "friends" etc.