How could they not know? She had been dating HF for four years. During those four years, he was arrested on various drug charges five times, and twice for stuff stronger than marijuana! And, once with the ex-BF as well!
Her last two boyfriends (that we know of) had drug arrests. The family didn't know? Come on. And, her instagram account that her mom also posted on had at least one picture of a reference to 420/marijuana.
Come on, folks. This can't be a surprise to anyone who had done even a little cursory digging on google. None of them hid their "party scene" well, I my opinion. And, in my opinion, they didn't want to hide it. In my opinion, they flaunted it.