I have a coworker I consider a mentor. Therefore, I buy him popcorn whenever I go to Costco. It is $7/bag for thank you and he will share if you want.
I have another coworker, I will aptly call, Karen. Karen will always tell me how she has a Costco card and hadn't gone. Karen is also a Popcorn Karen and will steal entire bags of popcorn and bring it up into her office.
This is popcorn I pay for personally. This is also popcorn that my coworker keeps inside or under his desk, so she is going into his personal space.
This isn't new behavior from Karen. She went into my desk to steal a half-eaten chocolate bar last year while we were going through a global pandemic. (Our boss is a big chocolate fiend and I guess he asked her if there was any chocolate while no one else was here). She also doesn't pay people back whenever they purchase her food or snacks.
This woman will be 59 years old on Friday. She is too old not to know better.
How do I politely tell someone with this much audacity to stop taking everyone's food?