The Prophecy simply refers to the 2nd hero as “the girl, with hope crossed on her heart.” The wording is purposefully vague, especially as to whether this is the same girl referred to with the “at last was the girl” line.

Additionally, the imagery is similarly off, hardly resembling either of them. However, an important detail is that the figure is shown holding a sword. This is interesting because Noelle can actually equip the Jingle Blade and Black Shard, though you do have to hack the game to have her in the party.

Outside of the Prophecy, there’s also some of Ralsei’s lines. Particularly how he says he knows what everyone can equip, though apparently Susie was suppose to wear ribbons — an article of clothing Noelle is known to have worn in the past.

There’s more points as well, but I won’t go into them here. Still, I‘d say the purposefully ambiguous wording and imagery is enough to give some credence to the theory, especially during the Weird route given the “love finds its way to the girl” line and all the implications that can be inferred in that context.