why is this information coming out now?
Maybe because this testimony was presented to a prosecutor's Grand Jury, and the prosecutor has a vested interest in keeping the police happy.
Maybe because a Grand Jury is inherently secret, so this woman had to be investigated by outside sources since all we knew at the time she was 'witness 40'.
Maybe because the prosecutor had no reason to bring up this woman's questionable history, & every reason to hide it.