About last night...not being pissed is a good thing. You really have no good reason to be...so it makes sense not to be. A bit disapointed...fine...that's okay....it's also okay if you tell her that you were a bit disapointed that ya'll couldn't chill last night...but that you understand. Trust me...you will gain far more "Brownie Points" by saying 'I understand' than by saying "I'm pissed".
And about not responding to the IM...that happens...she probably does have a bit of a question about whether you ignored her...but given your prior talks with her...she probably giving it a 50/50 bet that you fell asleep...
Whatever you do...be real. It's fine to get advice...to ask others what they think...but ultimately...be yourself...if she falls for you...you want it to be the real you...not an illusion.
and by the way...she knows exactly what you're hoping for with the 'make it up to you' line....(doesn't mean she's gonna give it up right away...lol....but it sound like it's sure crossed her mind!)
Good luck...have fun...and don't turn into a dick...you're doing good so far.
If you don't talk to your cat about Catnip...who will?