Umm...a few suggestions:

-forced to lick your boots

-whipped and made to count the lashes and repeat humiliating phrases after each one ("Three! I'm a spy cunt! Four! I'm an English whore!")

-spat wet and heavy in the face (a very hard limit for many people, a quite humiliating act)

-refused to wash or clean herself if it's a long session

-tie her tight on a chair and treat her/speak to her like she's a prostitute, shifting between cuddly & caring, enticed and ruthless cold. Since female soldiers and spies have sometimes relied on their sex appeal to do the job it's a rather natural idea.

-tie her strappado with hands hauled up behind her and feet/knees tied together, insert a powerful gag making her face strain and look slightly animal, then spank her and tell her she will be used as a sex toy (playing out the verbal threat could be very hot even if you both know it's only the two of you)

-invest in a black rubber hood with holes only at her nose and mouth, maybe a ring gag too, so her face can be muted into a black globe with a fuckhole. Hoods are very common in r/l breaking of POWs, and they can be very eerie in feeling (I have barely tried them myself, it definitely requires some weaning to)