The Other Gia

This is about a woman named Gia who finds a parallel world in her family home and in a room she sees her dead brother and father and they can't hear her when she speaks to them. When she hears her brother say he's going to New York on assignment Gia knows she must save him because that's the way her brother in her time died. She enlists the help of Colin Fenmore, a scientist's son and together they cross over, with Gia impersonating the other Gia; who died in a boating accident. All goes well until the other Gia's killer finds out she's there and sets out to finish the job.