For me it would be a mix of 5 and 6.

I love the length of 5.

But 6 edges it for me, because of the color, thickness, and mostly just because of the sheer volume of her hair, especially at the ends. Just see how much it spreads out. I would love to brush her hair, just to see it become straight at the ends as the brush goes through, and then see it automatically return to its natural position and position, including the waves, after being released from the bristles of the brush... This hair would really make a GREAT ponytail too - so thick, bouncy and fluffy.