I just told DD1 that it wasn't very nice to say those words.
Told her I know mummy does it sometimes & I shouldn't but please don't you do it, coz people don't like it. & she started telling us off instead.
DD2 is a bit different. different child. We just ignore her. She's also just found the naughty finger. We ignore her & it seems to be working, but DD1 can't ignore it, so she does it to her all the time, just to get at her.