My answer is no and especially if she advertised she has it on the menu. that said ...
Years ago, I saw a provider regularly and she appeared to be low volume and she mentions she was "fixed" and couldn't get pg. Now after a while I talked her into BBFS and it was fantastic (she was very tight). Now if I knew she was having BBFS with other (or most of her clients), I wouldn't have done it. I agree with CB's early assessment, and I was probably deluding myself that I was the only or 1 of a few. What can I say ... I was pretty new and stupid in the hobby. Luckily, I never got anything.
I haven't done it since. Also, I don't do DATY with most providers I see because you never know ... (again see CB's earlier post).