As far as I can tell, she's the mascot for a brand of salt. I could be wrong though. And she's in a bunch of videos on niconico. The only source for the name "Mirenmachi Hakata" is a translation note on post #462938. Name could also be Hakata Shio, according to post #407852. (Yes, I know shio is just Japanese for salt.) On Pixiv, she is also called Shio-tan.
