It's definitely a female, with 110% certainty. See how those two tiny 'sorta cone-shaped' preflowers come to a point? Those are what you look for when identifying females, and that's where a pistil will sprout out soon. Also, don't bother trying to pick off the balls of those males, because they are true males, and will never produce any bud. Use it as a mother, and 3 weeks from now you'll have a handful of females coming. You can also throw it into bloom after you cut the clones off, and end up with a nice main cola(or a couple if you topped it).