Jasper and Edward sure went brain-fried by their mate connection.

Yeah, everyone in the car except for David and Elspeth was completely driven by a single emotional imperative (Jasper: Save Alice! Edward: Find Bella! Allirea: Kill Demitri!) and they were all using their knowledge of each other's emotional imperatives to try and manipulate each other.

It's kind of a bleak scene, made possible, I think, by Chelsea. I mean, Edward makes a token noise about how Bella wouldn't want Elspeth used as a distraction in battle, but he doesn't feel the need to protect his daughter. If he did, he'd never have agreed to Jasper's plan. And in fact, if the normal bonds of family still held between Jasper and Edward, they each would presumably have been a little slower to risk the other's life so casually. But as it is, Jasper, Edward, and Allirea all feel they have nothing to lose, so of course they're willing to gamble everything on a risky plan.