I agree with candc. We all grieve in different ways and there is no wrong way. When my grandma passed, I lost it. I think part of it was because she was the 1st person in my family that had died. I cried for days, then it became less often. I tried to concentrate on all the good times we had. I would look at pictures and cry a little, then smile thinking of her. Also she was very sick and I tried to remember that she was no longer in pain.
I think everything you are going through is completely normal and appropriate.
Remember she will always be with you and eventually you will think of more happy thoughts of your grandma,and smile more than cry.
Hang in there!