This isn't from Negima. This picture is from a Ken Akamatsu series A.I.LOVE. In fact I believe this is from the cover of the first volume. May have been featured in volume of Negima, he did that picture in one featuring every character he created.

well, almost every one of his female characters looks the same anyway, does it really matter what they're labeled? -_-

He's created over 45+ female characters in just three manga and a few extra stories, atleast label it Akamatsu.