JerseyToughGuys
Tough Guy
Then Jamie ties it up and confirms it in his chapter. More or lessokay...it's not there for the slow witted, but...it's there.I only "missed it" because it isn't there. There is plenty of evidence he was communicating with her mother *after* the event which might be what you are thinking of.you must have missed it.
From ASOS, Tyrion III
"A maid of sixteen years, named Jeyne," said Ser Kevan. "Lord Gawen once suggested her to me for Willem or Martyn, but I had to refuse him. Gawen is a good man, but his wife is Sybell Spicer. He should never have wed her. The Westerlings always did have more honor than sense. Lady Sybell's grandfather was a trader in saffron and pepper, almost as lowborn as that smuggler Stannis keeps. And the grandmother was some woman he'd brought back from the east. A frightening old crone, supposed to be a priestess. Maegi, they called her. No one could pronounce her real name. Half of Lannisport used to go to her for cures and love potions and the like."
"It would have been kinder to leave her with a ******* in her belly," said Tyrion bluntly. The Westerlings stood to lose everything here; their lands, their castle, their very lives. A Lannister always pays his debts.
"Jeyne Westerling is her mother's daughter," said Lord Tywin, "and Robb Stark is his father's son."
This Westerling betrayal did not seem to have enraged his father as much as Tyrion would have expected. Lord Tywin did not suffer disloyalty in his vassals. He had extinguished the proud Reynes of Castamere and the ancient Tarbecks of Tarbeck Hall root and branch when he was still half a boy. The singers had even made a rather gloomy song of it. Some years later, when Lord Farman of Faircastle grew truculent, Lord Tywin sent an envoy bearing a lute instead of a letter. But once he'd heard "The Rains of Castamere" echoing through his hall, Lord Farman gave no further trouble. And if the song were not enough, the shattered castles of the Reynes and Tarbecks still stood as mute testimony to the fate that awaited those who chose to scorn the power of Casterly Rock. "The Crag is not so far from Tarbeck Hall and Castamere," Tyrion pointed out. "You'd think the Westerlings might have ridden past and seen the lesson there."
"Mayhaps they have," Lord Tywin said. "They are well aware of Castamere, I promise you."
"Could the Westerlings and Spicers be such great fools as to believe the wolf can defeat the lion?"
Every once in a very long while, Lord Tywin Lannister would actually threaten to smile; he never did, but the threat alone was terrible to behold. "The greatest fools are ofttimes more clever than the men who laugh at them," he said ...
in before the "Tywin wasn't surprised because he had already arranged the downfall by the time he heard the tale...but he didn't arrange the downfall prior to Robb meeting Jeyne" 
He could have just had her killed. They got paid for setting the trap from day one. You need to reread.
Starting from page 1 of this thread.
