The Quality Street Girls by Penny Thorpe

At sixteen years old, Irene ‘Reenie’ Calder is delighted to land a seasonal job at Mackintosh’s Quality Street factory but trouble seems to follow her around and it isn’t long before she falls foul of the strict rules.
Diana Moore runs the Toffee Penny line and has worked hard to secure her position, but Diana has a dark secret which if exposed, could cost her not only her job at the factory but her reputation as well.
When a terrible accident puts supply of Quality Street at risk, Reenie and Diana know that everything rests on them, if they are to give everyone a Christmas to remember…