She's a force to reckoned with specially in PVE. If she is outclassed in terms of speed/agi she will die instantly in PVP. Place her on a suitable position wherein you can kite your opponents effectively.
Flare is definitely a tank killer and dishes out massive damage with a slow casting time even Lv.20 Magic Guard + Lv. 20 Providence combo doesn't do much.
If you want her to excel in pvp specially in match battles I suggest to buff her with Casting Time -60