The profile of the character looks like exactly like Karen, a Dark type elite four leader from the Johto league. Dark type leader using pure dark type darkrai? same profile? It's probably Karen.
And yeah, she will face Ash in the finals however.. I hope Darkrai owns ash.. :\
If Ash had a Honchkrow, he could beat Darkrai, seeing that Honchkrow is the best Darkrai counter in the game; immune to sleep due to insomnia ability (dark void darkrai's signature move) and takes half damage (resists) from dark moves.. So yeah. Karen and I hope that Darkrai owns ash when karen battles him.