My sister's Doppler effect is irritating!

can't my sister stop yelling out the car window?
she yells stuff like: "I love my sister!" / "I love Mom!"
especially when pedestrians are nearby..
(walking around, or at crosswalks / stoplights)
the Doppler effect will apparently scramble the sound..
but I just wish she'd just STOP IT IMMEDIATELY..
it's just so embarrassing! (and she knows it well)
not to mention that it's annoying as all get out..
hasn't done this in some time, either.. she'll be gone soon :)