Well, New Blood is from 2015 and thus canon under 343. And won't do if we disregard all 343 canon.
So we need a source from when Bungie held the reins that answers definitively whether Noble 6 is, regardless of player choice, male or female.
Even my Halo encyclopedia from 2011 is published with 343's logo on it ... they took over Reach roughly a year after launch. It refers to him as male. Now, being reasonable, they were most likely busy with Halo 4 and wrapping up CEA, so I doubt re-writing Halo lore was their priority. Perhaps that was Bungie's intention to have 6 be male. Perhaps 343 went with male as male is the default in the game and the male asset was used as Noble 6 in the promos. Perhaps they flipped a coin.
Much of the stuff prior to that (the game guide, game manual, Halsey's journal, etc.) seem to be pretty ambiguous as to Noble 6's identity, if they mention him at all. So perhaps Bungie really wanted that character to be left to player interpretation ... which in sci fi is not something canon-obsessed fans particularly like. But for the sake immersive video game play, some do. Who's to say? Maybe I missed something.
However, for someone who wants to disregard 8 years of canon and fancies Master Chief is still floating in space in a cryotube, I don't see why you need anyone or anything to tell you what Noble 6 may or may not be. If you want to go strictly Bungie, from what I just dug through, nothing identified Noble 6 as anything but Spartan B-312 until 343 took over a short time after Bungie released the game. But again, I could have missed something.
I guess, to summarize ... and don't take this the wrong way ... you're already changing Halo lore to your liking (i.e. Halo 4 never happened), so let Noble 6 be who you want her to be. It's not like Bungie didn't give you the option to do just that.