Uk employer - French employee working in France - reducing days per week

I have recently joined an organisation following a four year career break to raise my daughter. I have reactivated my cipd membership and believe I am doing well in my new role. However, I am seeking some advice on an area which I do not have any experience.


Within my company, we have 4 member’s of staff based in other countries. We have one French lady working in France. She has worked for us for 7 years and we/she have her offer letter / contract of employment (all translated) and signed. Although I am very aware that her role also falls within the constraints of the labour law, French constitution, case law etc.   Any other correspondence i.e. training agreements, sales target letters are all in English & signed by her.


Last week she contacted her director to say that since the market is not very busy, she would like to look at reducing her days per week (annualised). This was not something we considered previously or in fact have had any discussions with her regarding the market in France & her role.


She has indicated that she would like to work a set number of days per year, depending on how busy the period is. I.e. 200 days per year.  We are happy for her to change her working days.


I am wondering how we would go about this process. Would it be quite simple (like flexible working) as the lady has requested this herself or would we need to go through consultation? As this is a request from the employee, would it be ‘an amendment to the contract of employment’ & a letter detailing this amendment would only be required (plus translated)?


Also, could this be set up on a fixed period, i.e. 12 months with a view to reviewing at the end of set period - so not a permanent change?


Also, would I simply calculate holiday entitlement as I would any other part time employee? I am assuming that the legally required 5 weeks per year plus stats would be pro-rata.


We have an HR system for booking holiday so we could utilise this to monitor her number of days worked.


Sorry for all the questions but any advice / process advice would be most appreciated.