i keep all those doc in the office as my husband and myself need to work, so no one at home in the daytime, i don't like people to see my personal things, so i just lock them in the office. re: the jewleys thing, just put them in the safe-box.
yes, i keep all valuables under lock, for other things, i also put them in drawers properly locked. For other letters etc, i put it in a box at home or at office.
you must also set houserules to include that your bun bun cannot open your drawers without your permission. So except for the closet or shoe cabinent, she is not allowed to open other drawers or cupboards. Of course, some bun bun might against the rules and open them. However, it is better state than nothing. In case you discover your bun bun steal looking your things, she is breaching the houserules and not performing duties in accordance with instructions.