Short texts could mean she is unhappy or pulling away. Or she is just really busy. It's the change in behaviour that is important.
I've read some theories that say if a woman is pulling away you don't want to chase her b/c it makes you look weak/desperate. But it really depends *why* she is pulling away.
My partner travels a lot for work. Early in our relationship, I was pulling away b/c I was missing him so much it hurt. I was increasingly short with him, he was busy and told me to 'take all the time I needed'. He honestly thought he was giving me what I needed (space) and I interpreted his communication as not caring. Turns out it was the same for him (hurting from missing me), so we got into this negative cycle.
We solved this by having a really deep discussion about our feelings and needs from each other. Which turned out to be *more* communication when one or the other was feeling lonely or stressed. If he had continued to pull back and we didn't have our talk we probably would have broken up (not for long tho, I suspect).
So you need to find out why she is increasing the distance. Ask her what she really wants, and you tell her the same. You need to be vulnerable in order to be happy. Good luck.
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh