Regina wants to believe – to remember – that Snow White really is an awful, unforgivable person, really she does… Sure, she was once a bratty little girl with an unforgivably big mouth. But unforgivable as a whole? Sometimes whatever goodness remains in Regina struggles to believe that – not that she pays those parts of herself any mind, of course.
She reminds herself frequently while under Rumplestiltskin's shape-shifting spell that she's here with Snow White to try to kill the girl – the no good, rotten, spoiled, stupid girl who always gets everything! But sometimes, when face-to-face with Snow, that's hard to remember.