No person ever has the right to receive a reference from a former employer and no employer is ever obliged to write one. (The only possible exceptions might be where this was written into an employee's contract or where there is an agreement between a trade union and an employer. Both of these situations would be extremely rare).
So, as far as the law is concerned, there's nothing you can do. Your only practical option might be to 'go above the manager's head' and approach her bosses.
However, CRB checks have nothing to do with employers' references, so the absence of a reference does not prevent you from obtaining a satisfactory check.
Chris