I'm sure this is a toughy. She possibly isn't sure of herself in the new family situation, and this may be her way of demonstrating that. I suggest a book called "how to talk so kids will listen and listen so kids will talk," by maislish and faber. it's fantastic, and teaches parents how to answer kids when they start begging, pleading, whining, etc, so that they feel heard, and then stop the behavior. It's an easy read - much of it is in comic book form. I've given this book as a gift a number of times because it's so great!