Perhaps if she’s a sailor, she wound up in this world during a storm?
Portals to other worlds are likely to appear in such chaos, and look like swirling vortexes of natural materials nearby, with light and music also coming from them.
So in a wild storm at sea, one forms in front of Samantha, made of lightning, wind, and water. A song comes from it, a peaceful tune drastically contrasting the chaos around her. Before she knows what to make of it, the ship is pitched by a wave and she’s sent forward into the gateway…