If you thought Taylor Swift popularized the monogram necklace, you're wrong. She's about, oh, five hundred years too late to be considered a trendsetter. It's Anne Boleyn who rocks a gold "B" necklace like it's going out of style.
"She pushed her French hood far back on her head so that her dark hair showed, and straightened the gold "B" that she always wore round her neck" (17.73). Yeah, once the necklace is mentioned, Mary can't stop talking about it. Is this paid product placement? Does Mary collect a check from Stella & Dot every time she talks about it?
Anne wears the necklace almost every day, and it's not because she's hard up for cash. As the king's mistress, she could ask for any jewels she wants (and she does: see below). No, Anne wears the necklace for a different reason. "'I am a Boleyn girl, a Howard girl,' she whispered, her hand on the golden 'B' at her throat" (48.10).
As the sister of the king's mistress, then the king's mistress herself, and then the Queen of England, Anne Boleyn shifts identities the way some people change clothes. The necklace reminds her who she really is. Once a Boleyn, always a Boleyn. But because we only see Anne's various personas, only she knows exactly what that means.