I doubt the Evie is much higher than half of the first group, as in the first group, two of the Evies have Rose Drop and one of the Lanns has the Laghodessa set. I believe it comes down to real experience as PandaSong suggested, as it was clearly not the first time the solo Evie faced the Blood Lord. I'm just still in shock that a group could take that long to clear a boss. I guess he is really tough to knock down.
Or maybe she wear Rose Drop just to distract us that she's around lv 44-ish? xD