This post had reminded me a bit of the situation that led me to find this site about a couple of years ago, so I thought I'd finally get around to posting it to get some others' takes on it.
I read something about Popular 80s Movie (P8M) being re-shown in movie theaters for two screenings only. My friend Beth and I are HUGE fans of P8M, though slightly too young to have seen it in theaters, so I was super excited and email her immediately saying we absolutely MUST go see this together. She was very excited too and agreed. I should also mention I was not being at all coy about my excitement. Suffice it to say, I was being a tremendous dork for the month leading up to the screening, so she knew this was a big deal to me.
Three days before the movie, I got a text from Beth that says "Guess what! Jen's going to be coming to the movie with us too!" Jen was a friend of Beth's that I'd met maybe twice. I have nothing against her, but I was bummed both because Beth had invited someone along on our outing, and also because it's harder/less fun to have a dorky adventure with someone you don't know that well. I was sitting next to my boyfriend when I got the text, and my face must have given something away because he immediately asked what was wrong. I read the text to him (he knew how much I had been looking forward to this) and he immediately said "Not cool." Which kind of tipped me off that this was Not Cool, because nothing bothers BF, and I tend to be way more uptight, so a lot of the time it's just me getting bugged about nothing. He suggested that I just tell her that this bothered me. I've known her for nine years, and we have a very non-confrontational rel
ationship (which BF knows). If she does something that bugs me, I just seethe, then eventually forget about it. But BF convinced me I should say something, so I texted back "OK. But in the future, please ask me first." (I don't know if that's PA. Everything looks PA in a text!)
The next day she contacted me through Gchat and asked if I was kidding about the text. I said no, that I thought we were planning something together, and it hurt my feelings that she invited someone else along. I really expected her to say something like, "Sorry, I didn't think that would bother you." Which wouldn't have been 100% satisfying, but at least I got it off my chest, and it wasn't as though at that point I would demand she dis-invite Jen. But instead she starts going on and on (I mean a LOT of writing) about how that was the stupidest thing she'd ever heard, and she didn't know anyone else who would expect her to ask permission to invite someone along to a public place, and just because I'd told her about the screening did that mean I was in charge of her now... stuff like that.
Beth also asked what I would have said if she'd asked me first, and I admitted that I probably would have said it was fine (to avoid conflict), so she could not see why it mattered, since both ways Jen ended up going to the movie with us. I said that was like stealing five dollars out of my purse as opposed to asking to borrow it. I would probably have said yes, so both ways she ends up with my five dollars, so what's the difference! She said the analogy was stupid (yes, she kept using the word stupid).
She eventually said that this conversation soured the whole thing for her and now she wasn't sure if she even wanted to go to the movie. Which was kind of how I was feeling. But I was supposed to meet up with her the next day to give her her ticket in advance, and I said I would still do that. I figured it was hard to interpret tone in a chat, and that once we were face to face we could smooth things out, and maybe I would at least get a non-apology ("Sorry you got upset" or something) and we could go back to our non-confrontational selves. But when I saw her she acted like nothing had happened. I didn't know how to bring it up without sounding like I was beating a dead horse, so I wimped out.
We went to the movie, and it was fine even though we were a little chilly toward each other. But it really did color my opinion of Beth. Like, every time I thought of inviting her to do something, I would remember her calling my feelings stupid and decide I didn't feel like seeing her, and the friendship basically died. Though I want to make it clear that the friendship did not die simply because she invited another girl along (that's almost a red herring) but because I told her my feelings were hurt and she basically said "That's stupid." Actually, if I hadn't brought it up, I probably would have seethed and forgotten, per the usual, and we would have remained non-confrontational friends for years to come. Darn my BF for encouraging me to talk to her like an adult!

However, my question to the community IS based on that inciting incident. Was Beth rude to invite someone along to an outing I'd set in motion? I'm inclined to say yes, based on people's responses to the post I linked above. I told this story to a few other friends (none of whom know Beth, for the record) and they all had the immediate reaction of "Not cool" just like my BF, but they didn't necessarily think it was
rude. Just not cool. I'm not so sure I see the difference.
In case it matters, we're both women in the US and 29 when this happened - so, too old for this junk, and also too old to be getting excited about a P8M!