you know, I always call Jacob her morphin, she used him to dull the pain od Edwards absense in NM and when Edward came back the pain was gone but the addiction remained and she simply wasnt able/willing to quit him cold turkey
I dont think she lead him on, I think he perfect the art of selective hearing and was reading into her actions what suited him. in a movie it is so clearly shown that he basically ignored all she did and said that didnt suit the picture he painted for himself