Quoting BG Secrets:" That is a great idea! Thank you so much."
With out MMC, we buried the body with a Japanese maple, so that they would become part of the tree and live on through the tree. I made a memorial statue (you could do a stone, too) and put it near the base of the tree. It really helped me to begin living the rest of my life and to bring closure to theirs.
You could just do a memorial planting of a tree and keep her ashes with you (if you decided you wanted to keep them) and get a personalized memorial stone off Etsy to put under the tree or flower. You can continue to care for it in her memory and give all your love into its care.
I'd also suggest getting a sky lantern, writing a letter to her and releasing it into the sky for her spirit <3