Matthew was obsessed over you, to the point it actually started to form into this sick, unhealthy mess, and was keen to do anything just to make you his property. But you were already taken, and Nina, your little sister, was aware of it. But she was still gullible enough to be convinced that you were dating Matthew instead, since he kept mentioning how much he loved you while they were both on the phone earlier. And because of her small amount of knowledge, she gave the address to Matthew.