Line Renaud, 96, WAS a collaborator of Piaf's though. She co-starred opposite Piaf in the movie Boum sur Paris (1953, wiki), so she counts. She also co-starred with Piaf in the 1951 movie Paris Still Sings (wiki).
Brigitte Bardot, 90, co-starred with Piaf in Royal Affairs in Versailles (1954, wiki).
Piaf also starred in an obscure Mexican film in 1958 called Música de siempre (wiki). At least 2 of her co-stars are still alive from that flick – American actress Tongolele, 92, and Mexican Golden Age child actress Angélica María, 80.
Mike Stoller, 91, co-wrote the music for her famous song "L'Homme à la moto", but as she covered the song rather than originally record, it's doubtful as to whether they actually collaborated.
In terms of people who duetted with Piaf, I think they're all dead.