In essence you get her and 6 Chainwrasps for 10 less points than a tomb banshee and 10 chainwrasps.
I'm not sure what to think. The rending scream isnt bad, but has a much lower damage threshold over a Tomb Banshee, and her spell seems like it will only work reliably half the time, and yet more overpriced chainwrasp fodder that you cant max unit size...
Something here Im not seeing?