I don't know. But if she does and refuses to admit her mistake, I'm just going to play along with her during the class and doing it the right way everywhere else :-) In my experience, unless your teacher is a native speaker, there's next to no chance of having a teacher who really knows the language and can use it properly, so the best thing to do ignore the teacher and learn on your own (Google and the WordReference forums are great for this). I can't remember the last time I actually paid attention in an English class (I mean those before college). I'd usually browse Reddit and Voat on my phone. Sometimes the teacher would ask me to do something, I'd be a bit confused, the teacher would then repeat what I was supposed to, and I'd do that and go back to Reddit/Voat. Never failed a single test  :-)