Hi
If she lived in Shepherd's Bush this would probably be the most likely marriage for Ada Matilda
Marriages Sep 1916 
Clark  John D  Stanton  Hammersmith  1a 526    
Stanton  Ada M  Clark  Hammersmith  1a 526 
Harder to track Emily as she only has one Christian name but if she lived in the same area as Ada this could be her.
Marriages Dec 1919   
Parish  Albert E  Stanton  Hammersmith  1a 780    
Stanton  Emily  Parish  Hammersmith  1a 780 
If they married at St Paul Hammersmith those registers are held by Hammersmith and Fulham Archives.
Wembley the London district is about 5 miles away from Shepherd's Bush so not exactly close by but not far away either. Again it might be worth contacting Hammersmith and Fulham Archives about girls boarding schools in the area as there doesn't seem to be anything easily found on a Wembley School.
These are the schools they hold records on, but they are less likely to hold records on private or charitable boarding schools.
http://www.lbhf.gov.uk/Directory/Leisure_and_Culture/Libraries/Archives/23452_Records_of_Schools_and_Colleges.aspRegards
Valda