Can unexplained meanness be symptoms of anything?

Like if a person is cold hearted....slow to show emotion or even say I love you to their bff could this be a sign of anything ? Other then insecurity or Overly Conceitedness because it's not like she's a straight up b*tch alot of the time she can be extremely helpful but like certain vibes I get from my friend like if Im crying she's slow to comfort me...when I upset her I REALLY UPSET HER ....she acts as if nothing affects her what could this be? Like was my friend the victim of any sexual trauma?