I think you maybe answered your own question; she wants you to move on and be happy, or your unconscious is using her image (and attached emotions) to tell you that that's what she would say... you already know that I think. I do think that people who've passed on can actually appear in dreams, it's happened to me a few times and I know it was real. Moving on and being happy isn't the same as forgetting and, once you do reach a kind of happy place with this, you'll be able to reflect more on the nice times you had instead of the loss.