I've seen this term being increasingly employed on SM. In August, glinner included the term in the title for a post;
A new low for Vichy Feminism
'Vichy Feminism' though has no definition. It's use perhaps gives away its meaning; Vichy Feminism might otherwise be known as 'Collaborator Feminism' where the self-identified feminist collaborates with the oppression of women and girls. Some individuals who profess to practice 'Intersectional Feminism' may also be regarded as collaborators.
That though is just my interpretation. As mentioned, there's no formal definition of 'Vichy Feminism'.
The 'Vichy' of course refers to the Vichy government established by Chief of State Marshal Philippe Pétain at the fall of France in WWII, leaving the Free French to fight for the Allies, whilst the Vichy government and its resources were dedicated to collaboration with the Nazi's. That collaboration included helping deport 75,721 Jewish refugees and French citizens to Nazi death camps. In 1942 the Nazi's took more direct control of the Vichy 'Free Zone', with Prime Minister Pierre Laval' government providing aid to them. Laval was executed at the end of the War.
There have been various efforts to apply terms to describe 'feminists' who collaborate in the oppression of women and girls, perhaps through their opposition to single-sex safe spaces, their promotion of efforts to erase the term 'woman', their adoption of anti-science perspectives, efforts to restrict or prevent free expression, attempts to associate non-compliant women with fascism or far-right interest. 'Handmaidens' - a term lifted from Margaret Atwood's The Handmaid's Tale (1985) is often used. I don't reckon it is accurate; the handmaids in Atwood's novel are unwilling participants in the regime Atwood envisioned. A better term might be 'Aunties' , in honour of the character Aunt Lydia, who is a Collaborator with the misogynistic & homophobic Gilead regime.
Another term regularly applied to collaborating/collaborators is 'Quisling' - a term garnered from Norwegian war-time leader Vidkun Quisling, who headed a domestic Nazi collaborationist regime during World War II. I've not seen the term used in concert with feminism - such as 'Quisling Feminism', but it might gain traction in-the-future.
As mentioned before, 'Vichy Feminism' is a term for those who identify as feminists but willingly assist in collaborating in the oppression of women and girls.
Examples of Vichy Feminism abound. In the UK alone, we could perhaps consider the Scottish First Minister, who has expressed the claim that she is 'feminist to her fingertips' to be a Vichy Feminist. The Conservative MP for Wolverhampton North and Chair of the Women and Equalities Select Committee, Maria Miller might also be identified as a Vichy Feminist.
Whether the term reaches mainstream usage is yet-to-be-seen.