A female child in a white, long-sleeved shirt is kneeling on a couch, laughing as her hair is sticking up.
A child laughs as her hair sticks up.
A female child is a child, and "laughs as her hair sticks up" is a rephrasing of, "laughing as her hair is sticking up".
Female child is a child, and laughs is a synonym for laughing.
A child who is a female, is laughing as her hair sticks up