@erogon, she summoned the spirit to ask him questions with the ghouls and the chimera not being intended but simply a result of opening the gate.
I dont think she is a necromancer as much she is using necromancy for the goal of asking questions to people that died, she was "obviously" the
bad guy until this chapter were things are now on a different context, take Magnus were because there wasnt much context we assumed he was killed and turned into a chimera but this chapter give the impression he retains his personality as a chimera that gives a different perspective, assumptions are just that and we dont know how he died.
However, its obvious something is happening beyond the Ghouls ... something more serious.