A Spirit?

My mother recently had a heart attack and was in the hospital having tests done. She says that since her very first day of being in the hospital, she has a ghost that follows her around. She says it is a transparent light that flows above her, no real shape to it, she calls it Casper(the friendly ghost). In the hospital, she thought that maybe it was a halluccination from the morphine they had her on. But she's home now and not on anything like that. And her ghost is still there following her around. Could it be a ghost, or something else?

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