She's been researching ways of deterring flies without doing them permanent harm.
It seems they're a lot like ants- and dislike sharp pungent smells. Rotting meat, yes. Eucalyptus and citronella, gemme outta here.
So I'm sitting eating my lunch with a bottle of eucalyptus oil to my left and a battery powered whirligig thing on my right- and between them they seem to be working because there were flies in the vicinity until I deployed them and now there ain't.