Sorry for your loss. I hope she didn't suffer right before she "went away."
I'm sure she treasures the times you've had together. She mothered you for a reason: she enjoyed mothering you. She felt vital because she helped you out.
I feel one of the best ways to remember people you were close with is by going to wakes. There, everybody reminisces about the person--the quirks, the funny stuff, the serious stuff. I advocate wakes, even though I'm not religious. Wakes could be cathartic events.