The feeling of being followed. The feeling of being stalked and watched by unknown is scary. That's how her life turn's out. She's just a simple person. She had a lovely cute little brother and new no one other than her little brother's friends. How can she being followed if she doesn't even socialize.
Or she was just putting it all in her head. She just misunderstood everything that she was just paranoid. But what if she hears him, at night? Whispering her sweet words while he kisses her neck? Then she'll never be paranoid.