Being from the future, Winn knew that Kara must go on a date with William to realize he is not her Lena. And then they wirh Lena will kiss it better and live happily ever after. That's all, folks! ♥️
"where is she?"
You can't ever convince me lena didn't on some level suspect kara was supergirl you don't spend all your time and resources developing something for someone you were recently in a huge fight with unless you knew that person means something special to you