If Sasuke really doesn't know her he would actually think that's confirmation she is related to shin
lol, no, that's just dumb. So far he is only questioning her which is reasonable considering his long absence and his recent encounter with Shin.
But if he doesn't give her a chance to explain and just attacks her thinking she is indeed an enemy, he would be really stupid, that's rash and hasty thinking, which is unlike Sasuke.
Wouldn't be surprised if Kishi does that though, he keeps making him look worse each chapter.