I am curious is she trying to get her sister back from the magical girl, or teaching her strategies to win against a magical wife?
It seems it's the former.
Not now... Ryou.Nee-san... I'm not a kid anymore.Momo will be coming home soon...You have lots of women as your vassals.So... will you make me one of your vassals too, nee-san?I want to be second only to Momo-san... nee-san.