Certainly long, thick hair is usually one of many signs of youth and health in a woman.
But there's one more thing when regarding LONG thick hair on a woman: Long hair is high-maintenance.
A woman who wears her hair long signals that she is more traditional than a SINGLE woman who crops her hair short to have time for her career.
This applies even to women whose facial characteristics benefit from short hair, as they need not always to cut their hair short to complement their features--growing their hair long, then wearing it up usually does as much for beauty.