I am so sorry, but sadly you have to accept that your d is now an adult and can and should make her own decisions and she will probably make plenty you don’t agree with. Having said that, hanging on to a high school bff may seem comforting when first leaving for college but your daughter may soon get busy and find some new friends as well. Also is this a bff or a gf? If the latter, it is still the case that many/most high school relationships don’t last beyond first few months of college. But best advice is to focus on other things that are relevant to you and try not to think bout your d’s social life which you can’t do anything about anyway. She will make mistakes as we all did or perhaps this won’t be a mistake for her.