what is this behavior called does it have a name?

So I had cancer back in 2022 my sister who is considered the "saint" of the family got really weird about it. She took this very stern cold and almost hurtful attitude about it. To the point that I simply no longer discussed it with her. Yet her friend who had a much lesser form of cancer she said "oh I call Lisa every day to check on her" I'm like what???? How stupid of me I find out that a lot of my current GI issues are due to Eagles Syndrome and I will probably have surgery, and I told her and once again she did it again. She did it to her son who's wife had preeclampsia and was admitted back to hospital after she went home and could have easily died or had a stroke. When I asked her was she on her way down she said in that cold voice...no she had to work and she was going down in 2 weeks as previously planned. And her son had no one to help him manage a new infant alone and his wife in hospital. This has to have a name is it narcissism? She sent me one of her cold sort of apologetic emails and I never responded and I'm not trying to be passive aggressive but I also don't' want to say something to her I will regret. Normally we get along and have a great relationship but when stuff gets tough she gets really weird!