Her Reanimated Gladiators imply the use of at least Create Undead, since no skeleton or zombie is going up against O-Chul. That's a 6th level. 14th level at that time (3/3/8) is not unreasonable, since by that point Redcloak was 17th (he first uses implosion crushing the resistance and mentions it as a new spell level).
Characters in OOTS are extremely un-optimized which makes it easy to forget this has been a story about characters who are on the upper half of the level ladder for almost it's entirety. The benchmark being V casting Disintegrate against the Young Adult Black dragon all the way back in comic #186, implying they were at least level 11 at that time.