I'm assuming she felt comfortable with no bra because there's literally nothing to see from the front. I guess she didn't realize it was revealing from the side/back
Also, I hate to complain cause it's nice we can finally see a nipple, but it's so quick, far away, and not the best quality.. you barely see anything. When I saw "nip slip" I was hoping for a lil better, but hey, you take what you can get