The vast majority of relationships fail right around the 6 month mark. Not just PTSD relationships, but all relationships. It’s just long enough for the frictions of personality and different lifestyles / life goals to become apparent.
So whether or not the Facebook thing and text messages were simply the straws that broke the camels back / indicative of much more pervasive issues / she realized that the 2 of you simply won’t work together long term? Or whether she’s overreacting to minor things and blowing them up into giant things? I couldn’t even begin to place odds on, much less be willing to wager.
In either case, however? Do you really want to be with someone who is willing to break up with you over a Facebook post or text message? If the minor things can’t be taken in stride, how would you expect to weather the major things that come up when blending lives?