I'm sure it burned your sister's butt that, by you ignoring her, it denied her the opportunity to do the ugly JW shun thing they so self-righteously love to do. Good for you! And bravo for not leaving early.
But I disagree with you just letting the whole thing go, like water under the bridge, without saying anything to the relative who sent you that text. I would have told them, in the nicest way possible, that it was a hurtful request. Perhaps write them a Thank-You card with a separate note inside?
Explain to them that you understand the uncomfortable position your JW relatives' intolerance placed them in, and that you understand she was only trying to accommodate everyone. Tell her that by you leaving early, it would have made you and your family look and feel like pariahs who had something to feel ashamed for or bad about. And that you would have missed out on enjoying the lovely time you all had, when you decided to stand your ground and stay.
I dunno, that's just the way I felt when I read your story. I wouldn't have just let it slide as if it were no big deal. It made me angry.