Susan,
I go through the same thing with my daughter. Its pure seperation anxiety. It change from what we feel comfortable with, then having to adjust. My daughter will be 19 in July, I have a son 13, but still the thought she goes to college made my anxiety return. I felt more comfortable with her at home, she has been around my disorder and deals with it more than my son. My husband works nights. So I went frantic when she left, knowing my son still could make a call if needed, but it was the change that disrupted me, its like having a curve ball throw at you. Not unlike moving, or shift changes in my case with my husband, that triggered it more during the night when he first started. However I realize my children need to continue on with education, friends, etc, and even though it was uncomfortable for about 2 weeks while it happened, the comfortableness has set back in, and it will for you also.
Oddly, the other day I tuned into the morning show called Starting Over on TV about women going through difficult times in their lives. One I could relate too. She has been in remission from Hodgkins for 22 yrs, and her daughter is at the house too, they are trying to work on there relationship, as the daughter is older and they basically are having a struggle. The mother said she felt like is just waiting for the Hodgkins to return all these years, and only knew how to take care of her kids. What was she to do now? She was so very distraught over her daughter moving and leaving. Very much how I feel at times, this is all I know being in the agoraphobic state Im in, I don't know of anything else to do....but to work on exposure and LIVING my life again, not have the same outlook for 20,30,40 years of fear of panic. Its hard, but Im determined.
Trish