According to The 72 Hours That Saved Malala: Doctors Reveal for the First Time How Close She Came to Death
The gunman ... asked for Malala by name, then pointed a Colt 45 and fired three shots. One bullet hit the left side of Malala's forehead, traveled under her skin the length of her face and then into her shoulder.
In the hospital, army neurosurgeon Col. Junaid Khan told ABC/BBC News that Malala was conscious but "restless and agitated." She seemed stable, and Khan kept a close eye on her.
Four hours later, though, her condition deteriorated. Khan realized the bullet had caused Yousafzai's brain to swell and that she needed emergency surgery to remove a portion of her skull to relieve the pressure.
"The part of the brain that was involved was concerned not only with speech, not only the speech centers but also those centers which are involved in controlling or giving power to the right arm and right leg," Khan said in an interview. "So contemplating surgery in this very sensitive area can have risks in terms of ... losing the speech or losing the power in the opposite part of the body, meaning the person can be paralyzed afterward."
Khan pushed Malala's father for permission. "There are risks," Khan said, "but if you foresee that this patient warrants an operation and if you don't do an operation, she will lose her life, then you're going to take all the chances."
The craniotomy began after midnight. Khan and his team removed a portion of her skull, removed blood clots on her brain and put Malala on a ventilator.
(source CBS news)
So it was a 45 caliber handgun bullet that entered her face on a downward trajectory and then entered the shoulder.
Also, according to Cranial surgery without head shaving Journal of Cranio-Maxillofacial Surgery vol. 37, pages 477–480 (2009):
Based on a series of 632 patients who underwent craniotomy without head shaving, we report the efficacy and safety of our simplified procedure
So it is entirely possible that when she had her craniotomy in Pakistan, little hair was removed.