I have always been close to my grandmother and I know her to be a kind, funny and honest woman, but I can't help feeling there is something odd about her experiences. Let me explain; I believe my grandmother to be psychic.
My mother is originally from Yorkshire and at the age of 19 moved to London to work. My grandmother (my mother's mother) was in Yorkshire with my grandfather and uncle at the time. At 3am, my mother was walking home in a fairly rough area of London, having been a babysitter/nanny at the time. At 3am in Yorkshire, my grandmother woke my grandfather up and cried: "Something's happened to Flossy [my mother]!" This was before the days of mobile communication, so my grandparents had no way of reaching my mother except for repeatedly phoning her landline, and my mother did not get in contact with them for six hours. She had been badly mugged at precisely 3am. My grandmother dismissed it as coincidence.
When my great-grandfather (my grandfather's father) passed away earlier this year at the age of 96, my grandmother urged my grandfather to go and see his father. It being six in the evening, my grandfather said he would go to see him the next morning. My grandmother seemed disappointed with him. My great-grandfather passed away at 8pm that evening, peacefully sleeping.
I know it may like not much, but when my grandparents moved into their house, about fifty years ago, they were only the second people to move in. Previously, a couple had lived there for about fifty years, moving in just after the house was built. The husband was devoted, even growing a rose garden for his wife. He was killed in WWII and the rose garden was left untreated. She died alone.
When my grandmother was moving in, she entered the front bedroom and was surprised to see a old woman siting on a chair by the window. My grandmother was not afraid, for she knew that the woman - clearly a ghost - was good. The woman spoke to my grandma, saying: "This is a wonderful, loving house. You will be happy here. You will have three children here. You will die here."
I myself have experienced ghostly activity and I do believe that I have had a past life. Is my grandmother psychic? Or is it just an odd coincidence? My grandmother did have three children in her house, and it is believed that the woman who lived in the house died in that very room. Thoughts please!
I also agree with Rook in your grandmothers case.
I've heard experiences almost identical to what you've described, that a parent has a feeling that something has taken place, only to find out later they are correct. I've had the same happen to me.
So Rooks explanation seems to fit very well.