Long time ago, I used to waste Virulent poisons and Daedric arrows on her, as I thought that she leveled with you. However, I learned that she always has very low hit-points, so now I kill her with whatever I want. One time I killed her with a casting of Fury and let Constance kill her.
I used my dunmer Mage to start messing with her at first I placed food all around her and then I used my favirote illusion spells to make her get scared and then I just used fury to finish her off by using fury on Constance (I mostly use illusion and alteration) (I don't know that many destruction and restoration spells /:) (I also love putting food around people and using telekinesis to kill dragons)
As a simple, well-meaning Dragonborn bard who had only recently discovered his new powers of the Voice, Volseig the Rambler had no intention to actually kill Grelod. He wanted to help the kids, sure, but he was certain that his silver-tongue could somehow convince the spinster to change her ways.
Instead, she only became more irate and belligerent, and even this infintely affable Nord could only take so much from such a clearly wretched woman. High off of the recent revelation of his destiny and his strange new powers, the rugged young skald decided to put the fear of the Thu'um into Grelod.
Convinced that a display of his Voice would be enough to intimidate the cruel matron, Volseig spoke the words of Unrelenting Force. However, he was still a neophyte, both in body and spirit, and had not fully learned to control his reality-shattering tongue.
With a thunderous "FUS-RO-DAAAAH!!", Grelod the Kind was blasted across her own orphanage. If the maelstrom-like force of the Voice hadn't killed her in an instant, her frail bones shattering against the hard oak wall surely did.
The Dragonborn instantly recoiled in horror at what he'd done, clasping his calloused hands tightly to his agape mouth. He approached steadily, trying to discern if any sign of life remained, but intuition and experience had taught him better.
As he turned to leave, the Rambler was beset by the glowing faces of the orphaned children. Behind them, the truly kindly Constance shrieked for dear life, cowering in a corner like a panicked skeever.
But the children.
The children looked up at Volseig with beaming smiles and bright eyes. They joyfully praised him and the escaped Aventus, praised them both for the unintended murder. They reveled at the sight of Grelod's broken husk, and openly admired the work of the sinister Night Mother that Aventus had invoked.
With his stomach cold and churning, and his skin covered in icy sweat, Volseig the Ramber darted out of Honorhall, out of Riften, as fast and as far as his legs could take him.