I am. 19 now, and ever since I was 10 I have dreams that my grandmother is dead. In real life she is healthy, not even that old. She is in her mid to late 50's. And I always dream I am at her house and she is a ghost. It is never the same dream exactly. It's always different people with me with different things going on. But she is always a ghost, and I am always at her house. About 35% of my dreams are like this.

What does this mean? Is she going to die soon? Should I be worried?

I used to have dreams like that about my great grandfather (he lived to be 100) and also my grandfather it was when he was sick but no one knew yet but he already knew but didn't want to tell anyone

While I cannot say if your grandmother will die soon or not, I will say that dreams are merely your subconscious fears and desires... ones that cannot (or are not likely) to manifest in real life, so you dream them out while on the astral plane. The meaning of the dream could be several things, however, I think that it has to do with loneliness. Are you and your grandma close? Or do you and your family see her as often as she would like? I feel that the meaning is due to either you or your grandmother feeling distant from each other, like you spend enough time with her. I don't know, it'd be easier for me to interpret if you lived near me and I could tap into your energy, but that's my intrepretation.