My older sister battled breast cancer for over a year, and she was able to overcome it. It was a shitty year, but she managed to pull through by August 2024.

Every year we alternate how we get together for the end-of-year holidays: One year we gather for Christmas, and the next for New Year's, so that each family (mine, hers) can get together every two years with the other side of the family (her husband's family, my wife's family). A little before Christmas 2024, when she was supposed to host the New Year's Eve party at her house, her attitude started to change.

This year it was my sister's turn to organize the New Year's Eve party, and on December 23rd, she decided to announce on the family group chat that it wouldn't be at her house, but instead they would go to her husband's cousin's house, and we were also invited to go. This annoyed me a bit because it was a very sudden change of plans for a party I considered a family affair, I called her to ask why the sudden change, and mentioned her that it was a bit annoying she announced it on such short notice.

After she told me it was because she thought it was a good idea and she wanted to celebrate until late because she hadn't really partied in a long time, I told her that I preferred not to go, explaining that my kids are too young for that and we didn't feel comfortable taking them to an unfamiliar house on New Year's Eve.

Then I told her that I considered this bi-annual occasion a chilled family thing, and I thought it was wrong to change the venue and take our whole family to someone else's place, to be with another family group we didn't even know. That's when she started raising her voice, yelling at me that she was tired of pleasing everyone, that she would do whatever she wanted to, and whoever wanted to could join her.

I never raised my voice, and I replied that it was a shame she felt that way, so close to the date, that if didn't want to spend New Year's eve as we always do, she could do something different, she could just say so and we would understand. That's when she screamed into the phone, telling me and everyone who didn't think like her to basically go fuck ourselves. At that moment, holding the phone away from my ear while she kept screaming, I thought I didn't have to put up with that tone either, so I hung up and texted her, "Call me when you calm down a bit."

After this, she left every group chat I was in with her. Now my sister is giving me the silent treatment, has blocked me on WhatsApp, and won't answer my calls. But she does answer my wife's calls and messages.

We've had a couple of family events since then, and she acts like everything is fine, like no harm has been done. When I asked her why she blocked me and had left the chats, she just said, "I don't like talking so much on WhatsApp." I didn't know what to say. "Oh" was all I could answer.

At one last event in February, she didn't talk to me much, but as we were saying goodbye, she hugged me and asked, "Are we good?" and wouldn't let go until I answered. I said, "What?" while trying to get free, and she repeated, "We're good, right?". I replied "No, we're not good. You've blocked me and I can't call you. Call me so we can talk." After that, she let go, and I was able to leave. She still hasn't spoken to me since then. I've tried to talk to her, but she doesn't answer.

Now my son's birthday (preschool) is coming up, and my wife and I were unsure whether we should invite her and her kids, but we think her kids have nothing to do with her attitude. My wife had to send her the invitation because I'm blocked, and she replied enthusiastically that of course they'd come! She even seemed cheerful.

I suspect overcoming cancer changed her outlook on life, and now she's taken the stance that it doesn't matter if she steamrolls others, and that everyone has to respect her without criticism... and because I let her know I thought her attitude was shitty, she's basically written me off.

I don't know how to handle this. Maybe I'm spending more mind and energy on this than I should. I feel like I can't say anything because she survived cancer, and I feel bad for thinking this way, wondering if maybe she has every right to behave like that.