how long is

...farther than her elbows? What a... (let's be nice here, Hajirah...) peculiar question.

here's a pic of just how long her hair is

In human form ( and mermaid its just easier to explain with her being human) I would say its about to her hips but it looks like it could be a little longer.

Longer then Tiana and shorter then Rapunzel. So I'm going with 4.6 feet.