It's a good start. I'm confused as to the interpersonal connections. Why watching William's (since we don't know his connection to Lady Sybilla) father (also connection missing)die be a torture for her? She's also a bit to introspective about what other men would do. I feel a bit too distant from this scene. Some reversing of the order of information might help the hook and flow.
If you started with:
William (insert title here), her (insert relationship her), had dragged her to the market square (or other place) to watch his father die. for me this was the hook
Her fingers were locked and her lips clenched, but Lady Sybilla de Nevers was not praying for (insert father's relationship to her)’s soul. It was her own sweet deliverance she craved. Probably William meant it as some sort of torture, or a strange penance to quell her venomous tongue. Other men might have beaten their wives or dispatched them to a nunnery. <---I'd cut this line and follow up on how her venomous tounge relates to a man's death. Yet here she was, bundled away into a corner like a toothless old crone with nothing to do but sit and sneer. <-- I'm not sure this helps either because it doesn't clarify anthing. Her bones ached from the sharp Lenten cold and from the weight of her unborn child.
The moments lingered lazily, determined to extend their lives. Time itself was making a mockery of what should have been a sombre occasion. this seems disconnected to me
If you focus on the moment, Lady Sybilla is watching a man she knows die, and hone in on a POV, you'd have a compelling start. What is she feeling about the situation? Is sorry that her "venemous tounge" brought the man low? Did it? Is she worried that she's married to a monster and what's going to happen to her and the baby when she's born? If you picked one of these questions and worked with it in the first 13 it might be easier to draw a reader in.
edited for bolding
[This message has been edited by kings_falcon (edited June 24, 2008).]