She lived in Mickey's Toontown Fair at the Magic Kingdom for a period of time before moving to the Petting Farm at the Tri-Circle D Ranch at Fort Wilderness. When Minnie Moo was living at "Grandma Duck's Farm" in Toontown, I had the chance to see her and snap this picture.
I have read that there is a plaque for Minnie Moo at the barn at Fort Wilderness. I'll have to check that out while I'm visiting this week! ;)