Hi Sammycat,
I think that losing ones parents, especially if they die at that age that is not old enough to seem like their lives have been long enough. I know how you feel, I lost my mother when I was in my mid-twenties a long time ago and over the years since then every now and then I think of how nice it would have been if we had have had the time to become close as friends, not just mother and daughter. Yes, we were close, but with her illness we just didn't have that opportunity. I am very grateful that I had the time with her that I had, but it doesn't replace that adult relationship that I missed.
Time does heal, but you will never get over losing her, you will just treasure that time that you did have.
Good luck and let yourself grieve for a little while longer,
craftyone