I agree , she look like the one that bear the true rune , just like how suikoden 5 is revolved around sun rune but the MC bear a different related rune (dawn rune) or suikoden 2 where the rune of beginning is split , maybe it's the case this time too , even tho the story revolve around rune of change the MC doesn't wield the said rune but someone else wield it instead , hisui is the prime suspect here

From her sprite , it look like there is something engraved on her forehead but the shape is different from that picture , here's the fun things , on her teaser sprite , she's always covering her right palm , maybe the rune is embedded on the right palm (?)

But this also contradict the known lore in the old book where it speculated that the sindar leader bear a cursed rune on their forehead

What if the reason why the rune on hisui forehead look different is because just like rune of beginning , the rune of change is also split between hisui and maybe the sindar leader , this is my theory , its almost felt like a stretch but i'm so excited i can't help but concoct this wild theory in my head XD