Becky Rosen was in love with Sam Winchester, anyone could tell you that. Anything that Sam wanted Becky would do; anything. If Sam had asked why she loved him so much she would have told him. If anyone else had asked why she loved the books and Sam so much; she probably would have decked them. If Sam asked, she would tell; even if she didn't want to. No one had ever asked why she acted the way she did, no one. Why she was obsessed with Sam or the Supernatural books, why she was who she was. If they had asked maybe they'd understand. But no one did.
Becky's life sucked, it was as simple as that. She was a freak and everyone knew it; a loser. No matter how hard she tried everyone left; even if she wanted them to stay. She got depressed, sinking into herself; she thought she was a waste of space, who wasn't worth it. The multiple break-ups didn't help, or the never-ending parade of fake friends and sympathy. Then Becky's dad did the one good thing that he would ever do for her; he bought her the first Supernatural book. She read it to make him happy, only to realize that it was quite good
She started picturing a life with them; a life she always wanted. Siblings who loved you no matter how many times you ran away or fought; and a loving uncle even if he did call you an idjit. People, family that came back no matter how many times they left; arguments when people didn't leave forever. Then she fell in love with Sam Winchester; he was like the missing piece. He was funny, nice, and handsome, and he was loved; maybe he could love her. She actually fell for Dean, but he reminded her too much of everyone who ever left; of all the guys who broke her heart. Who promised to fix her; only to leave her more broken. He was the fate that she was trying to avoid; the only love she would receive was from an intimate object. Sam was the only boy who couldn't turn her down, or crush her into a million bits.
Sam could love her; and care for her, and take her hunting. Sam would care because he knew what it was like to not have love. Sam would be understanding; even if he got her killed if would be worth it. Sam would make her forget all the guys that ripped her up and spat her out; Sam would be kind and funny and understanding and great in bed. Sam stopped how much she hated herself; Sam wouldn't just be the next guy. Sam would treat her right; Sam would kiss her scars and be a dream. She could be friends with Dean; maybe he'd accept her. Maybe she would have a family.
That's why she was obsessed with Supernatural. That's why she was obsessed with Sam, and why she was desperate for love. If Sam had cared enough to ask that's what she would have said. Maybe he would understand; they all would understand. But he didn't ask. So she was left to pick up the pieces, standing all alone like she was used to. She forgot how much it hurt.