Who is Betsey Cavillieri from Roses Are Red and what is their importance?

Betsey Cavalierre is an FBI agent. She is in charge of solving the series of robberies/murders which detective Cross is investigating. They work as a team, each with a slightly different background, skill set, and professional jurisdiction. Betsey is single and invested in her job, though she would eventually like to marry and have a family. She describes herself as an overachiever, who has sabotaged relationships in the past. Betsey is undeniably attracted to Agent Cross, and they play the part of flirtatious co-workers for much of the novel. Eventually they do embark on a romantic relationship, and although they enjoy their time together, they make no commitment to each other. While at work they are entirely professional. Late in the novel, Betsey becomes one of the Mastermind's many victims and is brutally slain.