Stace,
It is okay to be sad that she is leaving. But....honestly..you should be happy...be proud...be excited for her! She is doing exactly what you raised her to do. She is spreading her wings...she is stepping out on her own. That is healthy, and good.
She isn't going forever away, and she WILL call you and she WILL miss you....eventually. Just be patient, do not expect a phone call the first couple of weeks or you will be disappointed.
She is going to make mistakes, it is how she learns. She will be fine though, she is a very smart girl. She is smart, beautiful and has an amazing personality. She will find her niche and she will make friends. Just continue being the good Momma that you are and she will come back around to you!