How to deal with a jealous (adult) step-daughter

She is 26 and has a child of her own, her father and me have been dating for almost 4 yrs. Her jealousy resembles that of a child, she dedicates poems, songs to him that talk about daughters instead of dad's, gives him pictures of both, calls herself daddy's little girl... she even went as far as to move two doors down to interrupt our privacy, i've really tried to have a good relationship, kissed her butt basically, but it seems that the happier we are the more jealous she gets. Read More: [http://answers.yahoo.com/question/index?qid=20090725224930AAf9qiT How to deal with a jealous (adult) step-daughter? - Yahoo! Answers]