Against ahri, When Ahri’s Charm is down, she has no real way of defending herself without blowing her Ultimate. Look to fight her when her Charm is not available.
 
Try and stand outside of the minion wave, but close to it. This will force her to choose between pushing with her Q or poking with it instead. Stand close to the wave so you can run inside of it to dodge her E.
 
Ahri is incredibly vulnerable when her Ultimate is down. Make sure you abuse the long cooldown early on. Against ahri, When Ahri's Charm is down there, she doesn't have a real way to defend herself without blowing her Ultimate. Watch to fight her when her Charm is not available. Try and stay outside the minion wave, but close to him. This will force her to choose between pushing her Q or poking with her instead. Stand by the wave so you can run inside to avoid her E. Ahri is incredibly vulnerable when her Ultimate is down there. Make sure to abuse the long cooldown early.