The municipality voted to name it "Les Blanchisseuses" (same name to be used in French and Dutch).

« La Commission Royale de Toponymie et Dialectologie a donné son accord pour l’attribution des noms tels que sus-cités en date du 02/02/2021 »

https://www.auderghem.be/00225032021A0007
https://www.oudergem.be/00225032021A0007

But to have it on OSM we need some evidence.  Because every time a street name is created or modified, it may take several months or years before street signs are there.

Nice if you can survey it and confirm the name is written somewhere.  And check if that is the real name (could be something like "Chemin des Blanchisseuses - Les Blanchisseusespad" or any creative variant they may have thought of).