You are right, of course. Just remember to do for your half-sister what you know she would not do for you.
If I were in your shoes, I would be tempted to limit visits, at least in the beginnning, but notification of hospitalizations and of course, death is important. That is, unless her doctor feels that visits by half sister would exacerbate her condition after visits. Sometimes doctors will discourage certain visitors for that very reason.
I also do not know what else to do to see my mom while she is still alive and I know I will not even be notified if and when my mother passes away or is in the hospital.
If I were in your shoes, I would be tempted to limit visits, at least in the beginnning, but notification of hospitalizations and of course, death is important. That is, unless her doctor feels that visits by half sister would exacerbate her condition after visits. Sometimes doctors will discourage certain visitors for that very reason.