He knew she had feelings for him and he wrapped her up in his silly games.
Archie and Betty had been friends for years. She had always hoped that one day her next door neighbour would start to feel the same way as she did. She had a crush on him for as long as she could remember. Trying to grab his attention any chance she could. She wanted to show him what he was missing.
One night they had decided to go to a party. Their friend Jughead had been pulling away so she decided to give into Archie and finally go to one of these parties he had always been talking about. He knew that he could finally get what he wanted out of her.
It was no secret, Betty's feelings for Archie. He even knew about it. Which made the whole situation worse. He picked her up and promised the best night of her life. She lost a bit of innocence that night and truly believed she was going to get what she had always wished for. Him.