They still dont know for sure if shes dead or not. They guys who make the show even said that on the Talkign Dead. Theyre just assuming right now, but they really havent talked about it or investigated. I think shes dead, but a lot of people are arguing it.
The phone was a total what the fuck moment. I know they did that in the comic, but Im not letting people tell me whos on the phone in the comic! I dont wanna possibly ruin it. My sister thinks that it might just be Rick going insane. I dont think theyll do that, but I thought thta was a cool guess.