Quoting Miss. Tiff:" <blockquote><b>Quoting jussttjessiccerr:</b>" last night my sisters water broke at ... [snip!] ... from everyone who is pregnant she may also feel resentment. In my thoughts throughout today. Strength for your sister."
This is excellent advice.
Also if you post pregnancy updates on facebook, talk to her about it first, and if it will upset her to see all the time, maybe block her from seeing those posts temporarily so that she doesnt have that constant reminder while she's grieving.