Make some users not be able to see online status

We all have that one friend that keeps annoying us but we don’t want to be rude to them. When they see that you’re online they know what you’re ignoring them. Just a small switch under the profile of users to make them not being able to see your online status, so they just see you invisible, but keeping it visible to others. Please add this my cousin won’t leave me alone please I need help.