Well, I don't know of any statistical reseach but maybe this piece of info will help you.
My daughter sounds very similar to yours. She was ready to start Kindergarten at 4ish, easy. She's always been ahead and advanced in language and math. Everything from birth was done early. Preschool was frustrating for her teachers because she would blurt out answers or whisper them to other kids and add further explanation to what teachers would say. She even schooled one of them on "medacognition" and in a borderline condescending way. (Her attitude adjusted with time and intervention but for a bit, she's was a bit of a know it all)
However, in our school district or state (not sure which is technically responsible for the rules/laws) they do not allow testing for early entrance. The cut off for Kindergarten in July 31st and her birthday is August 3rd. 4 days difference. Beyond frustrating. It doesn't matter if they're advanced, they simply don't start unless age guidelines allow them to. So she couldn't even start until she was * six*. This was rough on her and me.
She was acting out, out of clear bordem at preschool. Don't get me wrong, she's a sweetheart, but she was bored and through no fault of her own. She'll be 7 and is getting ready to go into 1st grade and already mastered the material for 1st, in Kindergarten. She is okay socially with classmates but that's her personality. She connects very well with other kids of all ages but most of her friends outside of school are 8 or 9 because she relates better to them intellectually.
So she really had the opposite problem as your little one. Her K teacher used her as an aide to other kids, really. She sat by kids who weren't quite where they needed to be in order to assist them. While it's my daughters personality to help, I'm not sure this was entirely fair to her. She was given more challenging work to try after she finished the regular assigned work everyone else was doing but this tended to make her feel like she was having to do more work than the other kids just because she could. Her teacher always made it clear it was optional but she felt obligated for a long time.
So if I had been given a choice, I would have started her at 5 or just barely 5. She would be going into the 2nd grade if she was able to start and this is where her maturity and academic scores make sense for her to be. I'm crossing my fingers this year will be better.
Consider bordem and all that comes with it. If your little one really can hold her own in Kindergarten and it sounds like she can, and WANTS to go to school and relates well to other kids, I honestly would jump at the chance.