WARNING: major spoilers below. If you don't want to read them, don't read my post. If not...enjoy!!
Panties? Nope. She asked, but she's like, "Dangit, that's NOT what I wanted to ask him!!"
Confess her love? Did that: eighth movie. (Is it the eighth? The airplane one, at least. With Kaito. When she had to drive the plane.)
Ask about his identity? I doubt it. Though that would be a very very interesting twist.
Spend time with him? That's what I voted for. As this arc focuses on, she's terribly upset about him going away for the first time. As such, she is getting really tired of it happening again and again and again. So, she is determined to NOT LET HIM GET AWAY THIS TIME!! She thinks that if she does not let him go, he won't dissapear. She vows to keep him at her side, but doesn't understand that it isn't his choice to dissapear. So, she's very very bitter with herself when she wakes up, Conan beside her.
Ask him about his feelings? I should have voted for that one. Because I'm sure that's what she was going to do. After all, whenever he calls, he acts like normal and doesn't hang up with a oh-so-romantic *fans face dramatically* "I love you" or something like that.
He hides his own emotions so that she doesn't miss him even MORE. (And I understand his logic. If she knew for sure that her love was returned equally *dramatic, sonoko-like expression on my face* then she would wish for his return even MORE than she already does. Which is hard to imagine but hey, its possible.) *Getting back to the point I was about to make* She wants to know if waiting for him is really worth her time. She wants to know if her feelings are returned.Other? "Ask him what the [BEEP!!!] kind of case is keeping him away for months at a time!!" *lol*