EDIT: Title should be "for giving", not "for NOT giving".
I'm (29M) in a discord server with three friends, Clara (30F), Clara's wife May (28F) and Clara's sister Bella (25F). Every once in a while, we get together to watch a movie together or watch someone play through a game.
Clara suggested a movie to watch, and after it was done, I logged it on my letterboxd (a movie-tracking and rating website). Bella noticed my rating shortly after I logged the movie, and in the call, said "you gave it two and a half stars?", sounding upset. I said "I'm sorry, it just wasn't really my thing". Clara and May seemed understanding, even though they loved the film. Bella was noticeably disheartened and quiet for the rest of the call.
After the call was over, I messaged Clara privately to tell her that I felt bad that Bella was upset about it. Clara was very blunt and said that I hurt Bella's feelings very badly, and that giving the film a bad rating before the call was even over was thoughtless of me. She explained that the film means the world to Bella, that it has influenced her greatly in her life, and that she wanted us to watch it as a group very badly. Clara said that she was the one who suggested it because she knew that Bella would be too sheepish to bring it up.
I apologized and explained that I didn't know what the context behind the movie suggestion was, and that I didn't know it was that important to her. Clara explained how she's brought it up before during other calls, and how some of her social media avatars have been from that movie. I admitted that I didn't pick up on those things, and that I wanted to apologize to Bella, but did not know what wrongdoing I should own up to. She said she didn't know what to tell me, and that she didn't know how I missed the memo on how important the film was to Bella.
I talked to Bella afterwards apologizing, and she said that she'd had a bad day, that she's sensitive to these kinds of things, and that everything had just piled up. She said it was okay and it was not a huge deal, and to not feel bad about it.
I do still feel bad for making a friend upset, but I have to admit I don't know if I was truly "guilty" of anything. My therapist has been trying to get me to understand what truly is my responsibility in a situation like this and what isn't, saying that I often take the blame for anyone who is ever upset because of something I did. I can't really see what is and what isn't something I should own up to here.
TL;DR - I watched a film with a friend group over discord and gave it a rating of 2 1/2 stars on letterboxd after we were done. A friend, Bella, who loves the film, noticed what I rated it afterwards and got upset. Her sister, Clara, who is in the friend group with us, was very blunt about over DMs how I hurt Bella's feelings and that it was thoughtless to give it that rating before our call was even over. I talked to Bella and she said not to feel bad about it, that she'd just had a bad day and she was sensitive to this stuff. Regardless, I still feel bad.