I have known for a long time that I only wanted my sister to stand up with me as my maid of honor/witness, because I have some abrasive friends/acquaintances who would turn a bridal party into something far more complicated than I want to deal with. I'm very happy with my decision, and so far all of my friends have been very receptive to the idea (no money spent, no time obligations, I still will spend quality time with them all but they can just attend as guests).
Last weekend, though, my FI's sister was acting strangely toward me and I found out later that she asked her mom "whether she was just going to be a guest" at our wedding. She is a few years older than me and got married last year; I hadn't thought she would even want to be required to stand up with me as a bridesmaid. Apparently though she is "stewing" over it so I'm in a tough spot. I have a younger brother and my FI is not having him as a groomsman - my brother is more than fine with the idea that he will be "just a guest."
I do not have any objection to having my future SIL as a bridesmaid, if it comes to that... but I just wasn't sure whether there was an etiquette-based obligation that I have to ask her. Plus, it complicates my "no bridal party" rule if I, you know, have a bridal party. I also just kind of feel like my hand is being forced - I have barely made any plans yet (we have been engaged for one week) so I could have been planning to ask her and she threw a pre-emptive fit when I didn't ask last weekend.
Are there rules about who you must have stand with you as bridesmaids? Am I violating an etiquette rule here?