I didn't kill her for mine, I simply accepted her request to kill bed of chaos and she presented it as a reward to me afterwards. --- http://backloggery.com/tancients New game coming to the US! http://www.youtube.com/watch?v=qnfLCyDs0cM
From: OmniNakago | #009 She simply gives it to you later in the game. If you kill her afterwords, she wont even drop anything (so don't do it expecting that you'll get another).
Yes. I think the only covenant you have to break due to story purposes is the Gravelord's Servant.
The Bed of Chaos and the Chaos Covenant are not really allied. The Chaos Covenant is trying to become human again, while the Bed of Chaos is an out of control failed experiment. Quelana is friends with "the fair lady."
It would certainly not break the covenant, for story reasons too.