Student or Learner
How should I interpret the sentence "She has light hair."
Does it mean that her hair is "not heavy, it is like silk" or does it mean "of fair colour"?
It would almost certainly mean "light-coloured hair", not the texture - unless the speaker is a hairdresser.
She is not necessarily blonde. You can have light red hair, or light 'mousy' hair.
There are some obvious imposters in the pics below - those with dark brown or black hair obviously don't have light hair.