Sister-in-law upset at MIL & I…

My SIL is very upset with my MIL and I right now.

As we know, it was Mother’s Day yesterday. My SIL’s first pregnancy unfortunately ended in miscarriage and she just finished passing the baby a little over two weeks ago. My MIL and I were unsure if it was appropriate to ask her so soon how she felt about Mother’s Day so we just didn’t wish her one... we both personally felt like it would be like rubbing salt in an open wound; ESPECIALLY coming from very heavily pregnant me.

That apparently was the wrong thing to do. She is absolutely furious at us. Not trying to invalidate her feelings at all, but at the same time I’m not quite sure what to do? MIL and I have apologized and told her we both thought it would be completely insensitive and hurtful to say something like that so soon after the loss. That just pissed SIL off even more.

Just trying to remember that she is grieving… I’m just not sure how to fix it? I feel like it was a damned if we do damned if we don’t situation…

Any advice??