Girl buys skates, doesn't understand what drives her to skate every single day and why her skating is improving so much. She really feels like a completely different person when on ice. Then a coach notices the skates seem to be just like those from a skater who had an unfortunate accident on the day of a big competition. Turns out the original owner of the skates was the kind to not let death stand in the way of doing nationals...
Another thing the girl doesn't understand is why a crazy old lady is coming to watch her skate every day until she's told this is the psychic voodoo priest mother of the original skater who did a ritual to call her daughter's spirit up, or the girl is told of the posession by some crazy old lady on the bus/street who tells her she will not have rest until she competes. Also, the girl tries to sell the skates when her grades begin to suffer but in a various series of strange coincidences, no one ever buys the skates. Meanwhile, girl's appliances all act weird. First the microwave sparks, then various lamps break, then her cell phone dies and her computer keeps crashing whenever she tries to skip a practice to play farmville on facebook or something. Eventually the girl has no choice but to "accept" the mission. We see her skate a large competition doing triples eventually, less than a year after she bought the skates and first stepped on the ice *grin*. Of course, we don't actually see her skate, we see the deceased skater.
Alternatively, girl's coach dies but doesn't stop coaching her...
Or, possibly, a bunch of skaters at a sleepover get together to do a spiritual seance conjuring up the spirit of a high level skater who died under suspicious circumstances. They didn't think it worked, but one of them got posessed...
BTW I think instructables has a how-to on a fake tombstone.