Tsunade goes down first because she is the least suited for free-for-all's. Ei chops her head off, Mei melts her down, Ōnoki Jintons her or Gaara buries her. Shortly after Mei goes down by Ei. The fight lasts pretty long from here, but eventually Ei cuts through Gaaras sand defence and Gaara with it. From there its Ei and Ōnoki. Ei continuesly dodges all Ōnoki's attempts at Jinton or weighing him down, and eventually lands a hit on a Ōnoki in the air. Ei wins by virtue of being the best suited for free-for-all combat. Mei nor Gaara are capable of even remotely impeding Ei. Tsunade is an easy target and easy to dodge, she won't land a hit. Ōnoki is dangerous, but Ei has got him beat in a battle of attrition.