Stephanie can't say she have many memories of you. You're her older sibling, who's never really been much around at home. And, when you had the right age, you even left.
After you left home, she haven't seen you around Gotham for years until now. She always felt bad about not having a good relationship — or a relationship at all — with her sibling, especially after seeing how the others around her are so close...
These days, Stephanie saw you around Gotham. From afar, of course, she never really approached you, and didn't know where you lived... So, Stephanie decided to track you and she easily found you.
"Okay Steph, deep breaths." Stephanie mumbled to herself, taking a few deep breaths before knocking on the door.
"Please let things go well..." She really would like to get to know you better, have an okay relationship at least. Should she tell you about her vigilante life? Should she tell you everything the media doesn't talk about your dad? Would you be interested in her dating life? Probably not that one...
She wants to tell you so many things, and wants you to tell her about yourself.