I found in a homepage a drawing of Minako drawn by Fukami Rika. Maybe Fukami Rika has done a mistake. Therefore some people write their names in unofficial ways. Hepburn is the name of an American doctor, James Curtis Hepburn. Kunrei system is similar to Nihon system, so Japanese people seldom distinguish them .
Hepburn system is much newer than that.
However, there are no suitable ways to express long vowels on Hepburn system. Therefore, they use exceptional and unofficial ways to describe long vowels like her. I've seen a lot of Japanese animation and video games that have little snippetts of English here and there. Not much, but enough to notice. I saw Hyper Police.