The tired thing actually makes sense to me. I've heard a lot of people whose accent will revert when they are tired/drinking. And she does get interviewed a lot after fights. I know that she is American, but I say revert cause she learned English from her Brazilian dad most likely?
Either way I'm happy for this thread so now instead of letting any thread that has to do with Mackenzie devolve into a discussion about her accent, we can just update this one.