from Comic Vine:
A hero with squirrel-like abilities and features, Squirrel Girl is not always taken seriously, but she has nonetheless defeated many of the Marvel universe’s greatest villains. She is a longtime member of the Great Lakes Avengers, and briefly served as a nanny for Luke Cage and Jessica Jones.
Squirrel Girl (Doreen Green) is a fictional superheroine appearing in American comic books published by Marvel Comics. Her first appearancewas in Marvel Super-Heroes vol. 2, #8, a.k.a. Marvel Super-Heroes Winter Special (cover-dated Jan. 1992), in a story plotted and drawn by Steve Ditko and scripted by character conceptualizer Will Murray.
First appearance Marvel Super-Heroes #8