in reality, these are all reasons why Mona is much more dangerous than she would have been if she had stayed at BR.
If she had stayed at the BR she could still have been blackmailed or helped in her academic career, her friendship with the other girls would have been a brake to any temptation to denounce.
She is now out of Burke and Quinn's hands, and fear quickly turns to resentment.
there's a saying, ‘keep your friends close, but your enemies closer.’
and anyway, yes, any ‘serious’ criminal, if he couldn't convince her, would have silenced her forever