Hello, I'm Retiring From Breeding Bengals. I Promised A Client

Hello,
I'm retiring from breeding Bengals. I promised a client I would provide stud service to her female one last time. This female had diarreha in the past and it also showed in her kittens, by a different stud. I requested a stool test from her vet first, and then agreed. However, I'm seeing that she has diarreha again. I don't want to breed her because she's ill, and I don't want to chance my male becoming ill. I really don't know what to say. Thanks for your advice. I should mention that this female is eating and drinking well and is active. And she's in a strong heat.
Sincerely,
Valerie