I had assumed that she was only half-werewolf, but maybe the Change is an adolescence thing? Or maybe she's what the Discworld series called a "yennork" - a creature who is a werewolf by species but can't shapeshift. Or maybe the author of these strips is just going for cute little vignettes and hasn't worked out all the implications of their story ideas (like the bit about Maria being originally sold as effectively a sex slave, and yet it's a world where androids have rights).