Hi waitingwife,
first

for handling a difficult situation in a way that it did not escalate in a much bigger way. And the conflict on one side did not spill over into a conflict with H either which was also good

. Neither did you hide it

. Dealing with difficult FOOs is not easy and it would be a miracle and actually more likely a sign that you are walking on eggshells if there would be no conflict that temporarily flares up. The fact that you took a strong position and let things fall where they may may be a sign that you are more aware where your boundaries are and are taking steps to protect them. While this is progress it also means you will for a time encounter more conflicts and have to handle those.
How do I deal with my hurt?
Is SIL close to you? I suspect not and then I wonder why whatever she said could touch you so deeply. From what you wrote she was disrespectful and crossed boundaries but maybe she touched an issue that needs dealing with?
Would it be justifiable to be NC with his FOO?
You could go NC however maybe this would be a B&W overreaction out of anger and hurt? Can you imagine ways to think about this in more grayish ways?
- SIL is not all of FOO.
- NC is for forever. How would a timeout look?
- NC is complete. How would a set of boundaries look that are fully under your control. What interactions would be safe?
But I want to be centered again before I can take on that trip.
Your own FOO likely will always stir thing up in you. Assuming you are not fully centered - what can you handle and what not?