What Is The Cause For A Child To Be Self-absorbed Who Does Not Tolerate Some Noises?

Hi,I am Jenny.I have a granddaughter who has behavioural issues which started quite early in her development but now she is at school have become more apparent.She is a very intelligent child but reacts differently to most children in a normal situation.eg some sounds and noises are not tolerated by her,certain clothing irritates her,he is inable to control her emotions and physical responses in stressful situations,she becomes quite self-absorbed and can play quite happily for hours on her own,she has difficulty understanding another persons perspective on things.It has become noticable at school as she is lashing out at other children because they do not see things in the same light as she does.She is being branded as a naughty child.She has bouts of good behaviour but is not sustained under stress.My daughter has 2 other girls who do not behave in this manner.She is extremely mindful of their diet and is reluctant to put her on any medication.I feel she has a form of autism,what are your thoughts.I am a registered nurse.