Backstabbing snake is probably too harsh. Like SerHawkes said, there is still a level, however small, of plausible deniability that she is actually being manipulative and not just continuing on as a misguided but well intentioned friend.
But I have absolutely lamented Ivy's personality changes over the development of this game. How her character has developed is up there with Stan in terms of how much I miss them from their earlier incarnations. I just choose to not make outrageous statements as though they're gospel the way you do.