@harveyfrancis,
I really doubt she's doing a "hard to get" game.
I'd guess it's more along the lines of, she likes you fine and enjoys texting/ snap chatting, but you're probably not the only one and there may be other people she's texting and snap chatting and low-key flirting with.
So now that things have become more pointed she may be reassessing a bit. Does she want to have a summer romance with someone nearby but not actually right there? Does she want something more serious? Is there someone else (either currently or potentially)?
Or, she may just be nervous! Texting/ snapchatting was easy and low-risk but actually seeing you takes things into another category and maybe she's just thinking more carefully about what she does rather than rattling things off.
Hard to know. You seem to have plans for Friday though so just keep those plans and go from there. (Do you have like specific plans -- where, when, etc. -- or just "yeah, Friday's good!" plans?)