Did I Say Something Wrong About Their Passing?

As-salamu alaykum, I really need some advice. I'm a 20-year-old female. I dropped out of university while C and the others stayed, so I don't see them much anymore. C often doesn't reply to my messages or calls, saying they're swamped with university projects, but I still see them active and chatting in other group chats, sharing memes and laughing. Recently a loved one of a close friend passed away - may Allah grant them and us a high place in Jannah. I learned about it through C, who told me. I wrote a condolence saying that the Almighty has relieved them from the hardships of this world, since I knew the deceased had been bedridden and my friend and their siblings had been caring for them. C reacted very angrily, saying I should be more careful when offering condolences and that my words hurt them and our mutual friends. They said they'd given me the benefit of the doubt before but wouldn't this time, then blocked me. One friend is ignoring me, and the other two I know are busy with their own lives so I try not to message them often. I honestly can't think of anything I said that would have been so offensive, except for one silly comment years ago during an oral expression contest - they laughed it off and we continued talking, doing projects together, taking group photos. I've never been to a funeral, I'm not good at socializing, and this is the first friend group I've really been part of. My family is introverted too. I talked to my mother and she thinks C may have been looking for a reason to cut me off and this was just the excuse. I don't know what to make of it and would really appreciate a third opinion. Edit: I checked old chats - C did confide in me after a friend of theirs died years ago and also came to me for support through fights with their mother. If I had truly offended them multiple times, why didn't they call me out then? Thanks to anyone who reads and replies.