So there's this 20 year old girl. I got her number by going direct during the day time. I could tell she was into me, had major IOI's, she even sent me the initial text.
We texted for a few days I setup a date, but she flaked the next day, told me thats she's sorry, but she couldn't make it or something.

Anyway, after a few days I texted her the "I just met your twin" line, which she responded to quite well. After that I decided to add her on facebook. Turns out we had some mutual friends etc...

Then the same night at like 1AM I get text "Are you asleep?", she told me that she couldn't fall asleep, we ended up having a pretty good convo.
That's a really short summary of the context NOW:

What does it mean when she text's you in the middle of the night with something like "can't sleep" or whatever?

I assume it's just an IOI. Maybe I should try to set up a day 2 even though she flaked the first time...

Well since it sounds like you built some comfort and hopefully maintained the attraction, you want to try to set up again. Don't be discouraged if it doesn't work out.

She's interested, get her out.