@NaomiRae,
It's rather normal to feel sadness, or even grief, at an upcoming separation with someone you care about. The more important the person is to you, the greater the degree of emotion felt.
It's also normal to feel a little bit of guilt when it involves your mother.
Eventually, your relationship will modify to the new dynamic. Both of you will grow, and how you behave towards each other in the first few months after you each go your own way, will determine the nature of the relationship you have in future (ie. if you want her close, keep in regular contact...etc)
Best Wishes.