A T'Bonz notes, in that flashback to her childhood, when she clearly starts thinking back to the attack and freaking out, Sarek is basically an inconsiderate dick to her - even if it's because as a Vulcan, he just can't grok what she's going through.
Maybe she received treatment later, but she was supposed to be in an irrational, agitated state after she got back from the EVA encounter with the torchbearer. I definitely remember fanon at the least at that time (some on this forum) claiming was showing PTSD.
I agree that she did not show any after the pilot, so this may have been a Fuller idea which was dropped.
Intrusive memories--flashbacks--are one of eight criteria for a confirmed diagnosis of PTSD. Also, intrusive memories are not necessarily pathological. People of normal mental health have them all the time (have you ever had a memory flash into your mind after you've smelled or tasted something? Well, that's an intrusive memory and perfectly benign.). By DSM-5 standards (and, admittedly, that is likely to've changed a bit in the intervening centuries, but probably not so dramatically as to be unrecognisable), she does not appear to have most of the criteria for PTSD.
It is possible she did have PTSD, but it was treated. Said treatment did not, necessarily, have to be at the hands of the Vulcans. I'm sure there are plenty of humans and other species (Andorians might be a closer match, emotionally, for the human personality) on Vulcan and/or Vulcan colonies/outposts. She might, therefore, be in remission, with only the occasional sub-syndromal symptom showing up from time to time.
Or it is possible that she never had any mental disorder at all. Remember, most traumatic events don't cause Acute Stress Disorder or PTSD. It's something of a trope that extreme stress leads to a stress or anxiety disorder.