I'd put pad locks on all cages....have her get her but over there to help, and if you can't find it. make her pay for not only the snake, but all the food it has consumed. next time she wants to handle something stand right over her shoulder and instruct her how to handle it, and when she puts it up make sure that she makes sure the door is closed and locked.
Friend or not, she don't seem to respect you, your house, or your rules very much if you have told her time and again to make sure the lid is closed.....sorry if I seemed hard, but IMO my snakes are like my "kids" if someone was puting their saftey in jeopardy then I would probably do alot worse than what I said..........
I hope you find your little IJ....
Neptune, Zion, Enigma,