That’s exactly what I did.
The ANPE (predecessor to Pôle Emploi) just dismissed my qualifications. They said “pas transférable” and that there wold be nothing for me.
You should ask for a French course for foreigners and, assuming the rules are the same as back then, they are obliged to help. I got a 3 month course for free which was very helpful as it was entirely in French and all sorts of nationalities, although predominantly North African.
She is likely to find herself directed to a cleaning job of some kind and although that sounds terrible it will mean she will be working with French people who are likely to have little/no English and will be forced to learn very quickly.
She should maybe also consider contacting the larger accountancy firms who have offices in the UK and France to see if there is anything available. As a CA she will know how to find them.
I wish her lots of luck because I know how it feels to have years of hard work just dismissed with a gallic shrug!!