So Ange is going to use an alias to avoid Battler from discovering who she is, because it would make him realise in turn she has come from an alternate future to aid him. Such a detail as how someone from an alternative future able to appear in the meta would before him would lead him to believing in magic again.........
........NOT. Battler has seen magic battles, red + blue text flying in empty space, a meta universe where he can observe the regular world from, another him running around on the 'chess board,' evil witch version of Eva, magical teleporting, hellish goat minions, female servents able to transform into stakes, magical teleporting, and a crap load of other magic shit. And yet he still doesn't acknowledge magic. It is utterly, totally, competely impossible to make him accept magic even with infallible evidence to prove it, because Battler IS a retard.
My point here? Ange should just say "Hi im your little sister from an alternative future," because it won't actually affect the shit that comes out of his mouth at the end of the day in the slightest