Sorry to hear you are so troubled. I think the advice to wait a while before doing anything may be very sound, as long as you don't wait too long.
By this I mean wait till you can talk about it without crying,
I have an unruly tongue and have often found that it helps, not to grovel or make an insincere apology, but to apologise for unintentionally having stepped over the line or said something hurtful. After all, you were expressing concern, weren't you, but it unfortunately was taken as criticism or as you poking your nose in, which I am sure you did not mean to do.
I would not myself wait more than a few days before sending such an apology, because in my family the situation is very likely to harden if I leave things longer than that, but your family may be different, so you are the best judge of when the approach should be made.
Not knowing your family, I don't know whether you would be better to approach your DIL or your DS or whether anyone else in the family can help out or not. It is probably wisest not to involve other members of the family, as if you do, your DIL and DS can say you are going behind their backs and that will just make things worse.
I hope you can sort this out and that you all can agree that you perhaps did speak out of turn, but the reaction was a little misplaced as well.