Incredible dream! You were given the old woman's power. You were using the elements earth and water to fight the enemies. Fire was also present (usually a good omen) in the dream and the running horse could be an air symbol. I'm not sure exactly what it all means but looking back at some of your posts I think you will be developing some super powerful psychic abilities and they are showing up first in your dreams, when you are most able to perceive them. Meditation will make the dreams even more clear. Keep a dream journal. Read up on interpretation.
The elements are used in many spiritual systems, shamanism, witchcraft, even Buddhism. You're part Irish so this is probably in your blood. How exciting!