How can I prevent (or catch) my mother and sister from snooping through my things when they come over?

When my mom and sister come to visit, they go through my drawers and shelves and find things to talk about. I don’t have anything to hide, it just feels invasive, and they have gone through personal letters to friends in other states and brought up personal info and feelings. My sister tries to say that letting someone go through ones purse is a bonding ritual, which is why I should let my neice (her daughter) go through my purse, as she has always tried to do herself. I have had to deal with this in the past, but they are due for a special occasion visit, and I may have to go to work while they are here. Just need ideas on how to prevent or sabotage these intentions. Thanks!