Eva is a Mii from the Wii.
Eva originally appeared as one of the 60 CPU Miis to be included with Wii Sports. Since then, she's appeared in Wii Sports, Wii Sports Resort, Wii Party, Wii Music, Wii Fit, Wii Fit Plus, and Wii Fit U. In most of these games, her internal ID is 058, however in Wii Music it is 23. Her Mii data filename is cpu_mii_058.rcd in Wii Sports, mii_058.rsd in Wii Sports Resort, Wii Fit, and Wii Fit Plus, mii_058.ffsd in Wii Fit U, and is cpu_mii_db23.rsd in Wii Music. Wii Party combines all 100 Mii data files into one larger file named mii_rsd.bin in the same ordering as Wii Sports Resort.
As with every CPU Mii, she does not have a creator name or birthday, and has Mingling turned off. Her Mii name in her Mii data file is エバ. In her Wii U/3DS-format Mii data file, she was originally created on a Wii (1).
Her Mii data file contains unused data. Her glasses are set to be blue (Wii glasses color row 2 column 1) and moved 3 down. Her mustache is moved 2 up. And lastly, her mole is set to be moved horizontally 3 right.
In Wii Music, her Mii data file is slightly different. While it's mostly the same as it is in Wii Sports Resort, it now includes a filled out Mii ID and console ID. Her Mii ID is 80-4e-9d-17 and her console ID is c2-3d-21-af. Her Mii ID tells us she was created on August 27, 2006 at 12:28:12 PM.
According to a September 2020 Nintendo leak about CPU Miis, Eva's nationality is Spanish (Spain).
In the files for Wii Sports, her dominant arm for Baseball (Batting) is left-handed, Baseball (Pitching) is left-handed, and Tennis is left-handed. Her unused dominant arm for Boxing is left-handed. Her Baseball Pitching style is underhanded. She's ranked 18 in Baseball, 4 in Boxing, and 4 in Tennis. Her group IDs are 8, 2, and 1.
In the files for Wii Sports Resort, her Wii country ID is 1, like all CPU Miis. Her dominant arm for Table Tennis is right-handed. She's ranked 24 in Swordplay, 1 in Basketball, 92 in Table Tennis, and 19 in Cycling. Her unused Canoe and Debug ranks are both 58, matching her ID value of 058.
Eva appears in promo art for Wii Music playing the timbales.
Names in other languages
Source: Wii Sports Resort