yea just take it easy and dont look into things too much, i'm in a similar situation right now. I've found with messages, that she tends to copy the number of x's i do, which is quite funny so i play around with it.
her taking awhile to reply isn't a big problem, just make sure you do the same. To be honest i find it annoying when girls reply straight away and expect you to do the same, as i hate messing around on my phone.
If i were you i'd text her thurs/friday, saying "i'm gonna be out tonight/tommorow night with my mates but it'd be nice to see you if you're going to be about so let me know if you are x "
that way you're showing interest but in case she IS playing games she isn't exactly saying no to a date, as you are going out anyway, and are merely giving her the oppurtunity to see you if she's clever enough to choose to. Catch my drift here?
if she says she cant meet up, but doesn't suggest an alternative time, i think you should put her on the back burner and go after other girls. If she likes you then the lack of contact should make her contact you. If not then you're busy chasing other girls so who cares?