You sound utterly shocked, OP. I would be too in your position. I would feel like MIL has done her darndest to split us up, she's done it and she's gone. I'd feel angry that she had the power to do that actually, that the relationship wasn't strong enough to withstand her thoughts.
It would make me think about D 'H' too... whether I would even want to find a way back and even whether I could... MIL's influence and wishes are still evident even if she's no longer around and how could I fight those now? It's one thing to have a battle when she's around but all bets are off now she's dead. I'd never have the chance to turn her around or make her see that I was a good DIL after all.
I'd feel that I have to support D 'H' on one level, but not all - not as a loving wife who can be depended on for complete and utter understanding. Why should I? The relationship that was, now isn't and that was D 'H's doing as much as his mother's. Still, for appearances sake I would do whatever I needed to to make sure that I didn't look back on my conduct with regrets.
Take time to think, OP, like Hamlet... step back, say very little that has any meaning other than platitudes and general supportive noises, until your D 'H' is over the worst of his grief and you've decided what YOU want going forward. Don't let that be his decision possibly cobbled together from a shared history with you combined with his grief and sense of loss.
Thinking of YOU and wishing your D 'H' well.