She is in a stable condition, report comes from her brother.
Sadly, it seems that is not the case:
He also addressed an earlier comment attributed to him, in which he was alleged to have said his sister was in “stable condition.”
“I don’t know where they got that word from. That is absolutely not even close to the truth. We don’t know. We hope for the best. We certainly do not know her condition, that’s why she is in ICU. I’m sure everyone wants to speculate but now is not the time for that.”
http://etcanada.com/news/190820/carrie-fisher-suffers-massive-heart-attack-on-plane/