Dark Miyu is a CPU Mii who apparently is a dark version of Miyu.
Wii Sports[]
In Tennis, her skill level is 2100 to 2200.
In Baseball, her skill level is 1600 to 1700.
In Boxing, her skill level is 1700 to 1823.
Wii Sports Resort[]
In Swordplay, her skill level is 1500 to 1515.
In Basketball, her skill level is 1705 to 1720.
In Table Tennis, her skill level is 1600 to 1630.