L.G.
Oh, this is normal! You have been a good mom, I can tell. I remember those days so well. Now enjoy a new hobby so that you can start letting go. Or start cleaning out a closet or drawer or some other project like photos. Do something that will make you feel good. Trust that your daughter will be fine. Your kids will be glad to see that you have a life outside of them.
When your kids come home, ask something good that happened today and something bad. That way you get a pulse on what they are feeling. In time, you will see that even your daughter will get through the good times as well as the bad times by coping with the skills you gave her. Let them know how proud you are that they can deal with good and bad things and if they are ever in a situation that they don't know what to do, to just ask you. They will appreciate that you trust them to handle things. Don't think you can protect her from bad things but be assured that she will be experiencing great moments at school. Enjoy those!
We have two children. In less than two weeks we will be taking my "baby" for his 2nd year of college. This summer was the first summer that our oldest, a daughter, stayed away for an internship (she has 3 more semesters of college). It is a sad time yet exciting to see them become the independent young people that we have raised them to be. They have had to deal with good and bad, but they both know they can call us at anytime and that is the best part.