It must’ve been hard to know that your sister was near and she didn’t visit you.

I wanted to ask you the same as @Open Eyes.
Is it possible that for whatever reason, you or her were distant.
I told you because I lived a pretty similar experience. I have been pretty distant from my siblings because of my psychological issues. I think they didn’t even know how to approach to me. I’m not saying this is your case. I’m stressing on the possibility that the relation went cold, without even have to blame anyone but the circumstances.

I would look for the right moment when you calm and tell her what bothered you and ask her what happened? Sure there’s an explanation and you may both clear things up and get an approach.