User blog comment:Maki Kuronami/Lesson 19: Robot? Whatevs. Relatives? HOLY SHIT./@comment-24177652-20140815010304

To me it sounds like Winter is Weiss's older sister. When Weiss was talkinf to that lady, she said that "I think your sister Winter is here." (Or something along those lines) Which makes me think that Winter has been away, and traveling. Or something.