I take no credit for this, as it is not mine but I felt it needed to be shared. I know I'm totally doing this!

1. I cast Soul Trap on Grelod. It does no damage, but is considered an act of aggression, so now she knows that she's being attacked. That's good; I want her to fear.

2. I attack her using the Mace of Molag Bal, the Daedric Prince of Submission. She dies instantly of course, but her soul is captured by my waiting Black Soul Gem.

3. I take Grelod's soul and I enchant it into a simple silver ring. The ring fortifies Restoration magic and magic resistance. I name the ring "The Eternal Penance of Grelod the Cruel".

4. I drop the ring on the pulpit at the Temple of Mara in Riften. Where it will be used to heal and protect those in need. For all eternity, Grelod the Kind's twisted black soul will be forced to perform acts of kindness.

thats pretty creative heh.

I just punch her in the face...

I just walked in, went straight to her face and shouted "Yol" and watched her fly into the wall burning to a crisp. Then I walked out laughing as the children cheered.