When my Mom died, and people said, "I'm sorry" I fought the urge to tell them not to apologize, as they didn't cause her death, ALS - Lou Gehrig's disease - did. But I understood what they meant, so bit my tongue.

I think the "right thing to say" varies person to person, situation to situation, and I AM sorry I cannot be more helpful than that.

Drop her a note in a few weeks, ask if there's anything she needs, even if it's as simple as a cup of coffee, or as taking care of her child for an afternoon so she can have some time to herself. And listen.