Is there a romantic way to say goodbye?

My girlfriend is simply killing me.
She is hot, tremendously. She’s sweet and lovely but she keeps calling me 50 times per day, texting all the time, and simply put trying to know whatever I do 24/7. I am not doing anything bad, never cheated, nor I intend to. I tried to talk to her about that, she agreed to relax a little bit, but that ‘little bit’ lasts usually one afternoon if I am lucky enough. I am not sure I still love her, because I am the kind of ‘independent’ guy who wants his vital spaces left intact. I want to be honest with her, and I think our relationship will not work however flexible I can be. It’s hurting me, but sometimes I discover I am pretending happiness while I am not, and that’s not fair to her in first place.

I do care a lot about her anyway, and I want she have fond memories about me. It’s not about being friends, it’s just about closing something in the less traumatic and more positive way, knowing that what we have been giving to each other was something extremely beautiful.

How can I say/do that without being misunderstood?