Longer is better. While a few women can pull off a short haircut (and far more can't), even on those women, longer is better. I mean at least shoulder length, but between the shoulder blades is pretty universally attractive.
I have long brown hair too that goes down to almost my belly button in the front and just above my butt in the back. My friend just cut her hair to about her shoulders from right below her boobs. I would suggest it because it can make your hair a lot healthier but I wouldn't cut it too short. I have considered cutting it as well but I am so attached to my long locks that I can't get myself to do it.