It might help having the passages in question, no?
FH in Dune Messiah wrote: Immediately, she [=Mohiam] decided to take the offensive, said: "So, the great Paul Atreides deigns to see the one he banished."
Paul smiled wryly, thinking: She knows I want something from her. That knowledge had been inevitable, she being who she was. He recognized her powers. The Bene Gesserit didn't become Reverend Mothers by chance.
"Shall we dispense with fencing?" he asked.
Would it be this easy? she wondered. And she said: "Name the thing you want."
Stilgar stirred, cast a sharp glance at Paul. The Imperial lackey didn't like her tone.
"Stilgar wants me to send you away," Paul said.
"Not kill me?" she asked. "I would've expected something more direct from a Fremen Naib."
Stilgar scowled, said: "Often, I must speak otherwise than I think. That is called diplomacy."
"Then let us dispense with diplomacy as well," she said. "Was it necessary to have me walk all that distance. I am an old woman."
"You had to be shown how callous I can be," Paul said. "That way, you'll appreciate magnanimity."
FH in Children of Dune wrote: Jessica glanced around the room, seeing eyes turn away. They were such seriously futile people that she found herself wanting to cry out against their ready-made justifications for pointless lives. Oh, if only The Preacher could see this room as it looked now!
A fragment of a nearby conversation caught her attention. A tall, slender Priest was addressing his coterie, no doubt supplicants here under his auspices. "Often I must speak otherwise than I think," he said. "This is called diplomacy."
The resultant laughter was too loud, too quickly silenced. People in the group saw that Jessica had overheard.
My Duke would have transported such a one to the farthest available hellhole! Jessica thought. I've returned none too soon.
Jessica was on Caladan and not present when Stilgar spoke; it's possible she could have heard word of it, but how likely? There were attendants, courtiers and guards present at the audience with Mohiam, so anyone at the court on Arrakis could eventually have heard about what Stilgar said, so the Priest could have been consciously quoting him.
I tend to agree with Amp: since Jessica probably didn't(couldn't?) know the Priest was quoting Stilgar, it was no doubt more his flippancy and insincerity that angered her.