kept him twisting away there
Ha ha -- good one, Celeste!
IMO, Lureen is not cold, calculating or manipulative. She saw Jack, understandably found him attractive, and went for it. That's what people are SUPPOSED to do, right? She may come on a little strong -- as does Cassie, later; neither of these women would have snared their cowboys any other way -- but that's OK. And she probably was rebelling a bit against her overbearing Daddy (evidence: first-date sex in the backseat of his car and, later, her smirk when Jack tells LD off on Thanksgiving). And she quite possibly was pregnant before the wedding. But none of those actions are particularly evil.
Jack, for his part, did not have an eye for Lureen. He grabbed her hat from the ground just to be polite (hmmm -- an echo of the times Ennis knocks Jack's hat off?), and probably would have ignored her forever if she hadn't made the first move. But she does, and he goes along with it much the same way Ennis later goes along with Cassie. Also, I think for Jack "money's a good point" -- the fact that Lureen's rich, while he's "nearly starving," is part of her allure. And he's probably sick of getting rejected by the Jimbos of the world. So eventually he just shrugs and decides he might as well get married, possibly with the further incentive of a pregnancy.
You know, I just noticed that her name is Lureen -- get it? She lures him. (Is there a parallel meaning for Cassie? She casts her line for Ennis? Well, maybe that's reaching.)
Anyway, Lureen and Jack have a good relationship platonically (better than Ennis' and Alma's, for sure). But over the years Lureen notices things. Jack is not the most passionate husband. He constantly goes off on fishing trips with his friend, for which he's willing to unilaterally drive 14 hours. He doesn't understand why women would get gussied up "just to go to bed" (nothin going on there!). She gets increasingly frustrated, keeps dying her hair blonder and blonder, as women in those days were commonly advised to do when their marriages were losing their zing. Eventually, Lureen puts 2 and 2 together. Maybe she doesn't quite get to 4, but let's say she's at 3 by the time of the dance. Her dancing comment may be a reference to Jack's sexuality, but if so it's a half-conscious one. She doesn't divorce him because she loves Jack, frustrated though she is.
Then the phone call from Ennis. Let's say, for the sake of argument, that Jack is murdered. By then she's at 4 -- she knows about his sexuality outright, either simply because of the murder or because it has become obvious in some other way to both the murderers and Lureen. That's why she sounds so rehearsed when describing the accident. Then, when Ennis confirms that Brokeback is a real place and mentions them herding together 20 years earlier, Lureen squeaks because by now she understands the nature of their relationship and realizes that Jack has been with Ennis since long before their marriage. Maybe to her, Brokeback stands for Jack's fantasy life, and Ennis' saying that Brokeback is a real place opens her eyes -- in other words, he really DID have relationships with other men. Ennis's final "we was good friends," another confirmation, causes another squeak and tears to well in her eyes.
And yet, despite all that, she advises Ennis to get in touch with Jack's folks. And says they'd like it if his wishes was granted -- "bout the ashes, I mean" (as opposed to his wishes about how he wanted to live his life). That was out-and-out kind of her, both knowingly (helping Ennis grieve) and unwittingly (leading Ennis to the shirts).
