I promise I’m not a terrible, crazy person but I feel like I’m the fiancée in this situation? My fiancé and I have been together forever, I have a huge, close extended family and my immediate family is me + 4 sisters+ 1 brother and parents. I also have a bigger social network than my partner. His family is him, his parents and 1 sister. I would say that in planning our wedding it didn’t occur to me to that she would even *want* to be a part of it. I have 4 “mandatory” blood sisters who would be attendants which, by my book, is already 3 too many. And while she’s awesome and friendly and I’m glad to have her as my SIL, she just never seemed to be the kind of person who wanted to be bothered with the whole thing. So I never made it a thing. When there are group text convos (me, her, him), I let them do most of the communicating because it seems most efficient? He knows my opinion, it’s his sister, and a million messages in group texting is hard to follow! Most of them time, I read and process and then forget/ am okay with whatever decision is made between them. I do this in friend texts too. It’s a combination of being lazy/overwhelmed and over extended/ and genuinely trying to make things more streamlined for others? I also tend to view a lot of my relationships very black/white, even if subconsciously. My siblings are *my* siblings, his are my in-laws. My bosses are bosses, not friends, and so on. As I type this I realize just how terrible I sound! But I promise, I mean no malice and never realized it could be interpreted the way you are interpreting your SILs actions. (I ended up going with no attendants for our wedding next year, before anyone other than he or I knew where my head was).