Not sure about Christmas day, as she called in sick.
But there are guidelines from the DTI regarding holiday pay for part time workers. They go something like this.
Part time workers (prevention of less favourable treatment) EC Directive on Part time work and (amendment) Regulations 2002 (SI 2002/2035)
This directive basically means.
If you have no 'full time' employees, you cannot be accused of less favourable treatment by reducing a part timers holiday entitlement.
BUT:
The guidelines indicate that you should offer part time workers a % of the statuatory holiday entitlement that a full time worker would get.
The guide amount is based on fifths of the normal entitlement.
SO:
The statuatory entitlement is 15 days per year.
If your part timer works 2 days a week, then 2 fifths of 15 days = 6 days holiday entitlement. 3 days = 3 fifths etc. (The amount of holiday pay is an average of the normal hours worked on each day)
If she demands - and you pay her for Boxing day - she loses one of her days - simple.
Part time workers have the same rights as full timers if any of their working days normally fall onto a statuatory bank holiday. So, if she normally works Christmas day, then she is entitled to holiday pay if you don't offer her any work. If you do offer her work, she is entitled to normal pay + holiday pay = Double Time!
But as she pulled a 'sickie' I am not sure.
Most of our work is on construction sites. They very rarely allow any work on statuatory bank holidays. So we don't normally have work and don't have to offer holiday pay to our part time staff as they can do the work on another day.
Try not to work at all on bank holidays (or just do it yourself)
Hope this helps...