I don't know about the "should" part of grief-- if indeed that is literally what she meant. Now a few years after my spouse's death I can say I recognize the phenomenon of the flutterings of happiness at some of the random memories, or times when I deliberately think about him or revisit his gravesite. There is still sadness at the loss, and I doubt that goes away. The sadness is not as painful or profound as it used to be, and I don't mind feeling sadness. It's just a feeling and so far hasn't killed me, and I don't experience it as negative even if it is typically considered a negative feeling.