Examine your reasons for sending her and her reasons for wanting to go to a boarding school. It’s an interesting dilemma in this day and age where there are more day options. In my “day” quite a few of my friends went away for high school but it seemed to center on several reasons: either the parents were busy and traveling alot so it was more stable not to keep the kids at home or they had gone and wanted their kids to go to the same place and one friend whose mother had died in an accident and one whose interests were so singular (music) that it just made sense to let them pursue outside what was available within driving distance. So I’d recommend going back in time to when this came up with your D and for both to re-examine the reasons why and see if you came up with the same conclusion to go/send away.