If you want to ask her what's up, why the distance, that's cool.
But, prepare yourself for potential overt rejection.
ENFPs are notoriously known for having people mistake their natural charm and interest for romantic interest.
And, honestly, persistance has never paid off for me, as in, when a guy I was not romantically interested in continued to pursue me, my lack of interest would not change.
I would not call myself a heart-breaker per se, but I think I have let a lot of men/people down, because they enjoyed my company, and I theirs, but I was not able nor willing to give them all of me, or a lot of me, or give them what they wanted from me.
Maybe she can sense how much you like her, and she feels guilty for not reciprocating the feelings?
I don't know.
But a decrease in enthusiasm during the courting process, in general, and ESPECIALLY for enfps is a bad sign, sorry, Kalach, it just is.
FormI, I'm not trying to be insensitive here, I am just being honest, and I don't think, granted, with the very little information you've indulged us with, that the situation seems hopeful. :/
I wish some other ENFPs would chime in, here.
I am just one girl, one ENFP, and this is what I read in between the lines of your story.
Now, if this girl were an INTP, or a T, I'd give you more uplifting advice/feedback.
But, I know how ENFPs generally do.
And, her being "terse" and markedly less playful with you via *text message* is not a good sign.