D.W.
What an unusual way of acting out. Maybe it is something that she has seen, you mention she know's what boyfriend and girlfriend are. I told my husband this morning that they are children and they need to test how far they can go and to see what respond it gets from you. If you respond in a negitative way then it has worked on her part. To try and reassure her that she is important in the family and what she does by making up stories and not telling the truth make you sad and has hurt your feeling. Instead she needs to help keep the family together and her part is very important.