That's a lot of things to deal with. Indeed, I don't think even medicine has claimed to have a cure for boredom. Perhaps your sister is intimidated by your exceptionally talented family, and feels there is little that she can do. You don't list the activities, interests, and enterprises in which your sister is involved. You mention that her last child is leaving home.
People often point to the empty-nest syndrome as a danger point in life.
But, more often, it is a relief for people. Sometimes, teens are not the best company at home. When that stress is removed, and with the free time and freedom of mind to pursue new options, this can be a time for your sister to reorient her life. It is good and important that you want to help your sister. You have asked about medical options for her, such as implanted antabuse.