I'm not sure, so I'll just throw a few names I can think of into the mix. I'm sure there's some stats man out there who can answer your question. Anyway, here goes - these are "of all time", not just those competing at the moment:
Betty Pariso
Linda Hoyte-Wood
Michelle Brent (Ivers)
Debi Laszewski
Gayle Moher
Yaxeni Oriquen
Annie Rivieccio
Andrulla Blanchette
Carmen Brady
Tazzie Colomb
Marja Lehtonen
Maryse Manios
Collete Guimond
My guess is that it's between Tazzie Colomb, Annie Rivieccio and Michelle Brent (Ivers), who all started in the mid 1980s - probably a 25-year career. I suppose it will depend on whether some of the aforementioned women (and others that others will put forward) were either competing as lowly (and unknown) amateurs early on in their FBB career, or in a "Masters" (i.e. older competitors) category at the end. I would say that the "longest competing pro" goes to the Taz.
Those who cannot be counted as they had a long career break:
Juliette Bergmann
Susan Myers
