My sister only cares about herself

Back in 2023 me, my dad, nmum and nsister had to move out and into my nmums jail bird friends 1 bedroom flat. When we were prepared to go there we took what we could carry in a taxi, my nsister took her jacket, phone and laptop and maybe something else, which im not at all mad about, but where the bullshit really comes is when had to go back to get the big stuff we left in the landing she never helped. It was always my nmum who is terrible under stress, my 60+ YO old dad with a hernia and me, who was sick from carrying really heavy bags down 6 flights of stairs and the stress. The whole time my nsister was out with her friends or just chilling in the 1 room shack and got defensive when anyone would call her out for it.