In your essay on Catelyn, you write: "Catelyn gives away both Robb’s hand and Arya’s, missing a hint that Walder would have settled for Edmure marrying one of the Frey ladies. (Note how focused Walder is on slights paid to him by Hoster Tully.) It’s just not a good deal that Catelyn made." This particular observation intrigues, due to its subtlety. Can you relate the textual evidence for this 'hint'?
Here we go!
[Walder Frey’s] head bobbed up and down. “Your lord father did not come to the wedding. An insult, as I see it. Even if he is dying. He never came to my last wedding either. He calls me the Late Lord Frey, you know. […] Your family has always pissed on me, don’t deny it, don’t lie, you know it’s true. Years ago, I went to your father and suggested a match between his son and my daughter. Why not? I had a daughter in mind, sweet girl, only a few years older than Edmure, but if your brother didn’t warm to her, I had others he might have had, young ones, old ones, virgins, widows, whatever. No, Lord Hoster would not hear of it. Sweet words he gave me, excuses, but what I wanted was to get rid of a daughter.”
-Catelyn IX, AGoT
Walder is speaking to Catelyn as Catelyn Tully in this interaction, rather than Catelyn Stark, and his preoccupation with the matter of Lord Hoster’s “slights” - specifically how he brings up a match for the still-unmarried Edmure - probably should have tipped her off that Walder would be sufficiently satisfied as grandfather to a Lord of Riverrun.
Now, giving away Edmure’s hand is technically well outside the scope of Catelyn’s authority as an envoy for Robb (acting Lord of Winterfell), but as we see with Catelyn’s call for a Great Council to Renly, she’s not shy to act outside the technical scope of her mission when she thinks there’s a need. At this point of the story, she’s also got Hoster to back her up (at this point he’s with it enough to give orders concealing the extent of his sickness - if Catelyn goes to him and explains, he’s capable of approving her actions and likely to agree with her reasoning).