<human>: Can you give me the gist of the text in a nutshell?

I've been looking at this chick at school for like a week. And I had a feeling she was glancing back from time to time. So I grew a pair and went up to her after class and introduced myself (her girlfriend was present, just for info). 

I walked up to her and said, in a rhetorical kinda way. 

"Hello, are you Katie?" with a smile on my face as I reached out to greet her. 
She smiled and replied 

"Yeah." 
As she said yes, our hands met and I proceeded to introduced myself without pause. 

"I'm John,  and I was wondering if you'd like to go out some time. Just you and me, like lunch or something?"

She was still smiling as she asked 
"oh, when?" 

"I don't know, tomorrow maybe, if you're available?"

"Uhm, I'll have to think about it okay? Because I'm going away soon so. "

"Oh, okay no problem, see you later." 
And we both waved goodbye.

I have no clue what she meant by going away. Did she ask "oh when?" to give herself time come up with a polite excuse to say no? What does it usually mean when they say things like "I have to think about it?"
<bot>: Asked girl out whom I've never talked to and she said she'd have to think about it. What on earth could that mean? I was sure she'd say yes judging from her looking at me from time to time.