My mother in law (Chinese) will be visiting myself and my wife in the UK over Christmas. She currently holds a visa for the UK so that's not a problem. She's applying for a Schengen visa and I was wondering if it's requried for her to have an invitation letter from her daughter which explains that she'll be visiting us in the UK and then travelling to France from the UK along with scanned copies of her respective documents for residence in the UK?
Thank you