I think its the wasp, and I think that she still loves Hank.
He's hurt her worse before now, splitting the roof of her mouth actually, and they've stayed together. She's probably forgiven him, and ever since Capt made an *** out of Hank, she's been getting close to him, possibly to hurt him eventually. Then they freed Bruce Banner.
Its either that or Betty Ross. She wanted to free Bruce, so she outed him to the media (she IS the PR manager), and then did her schtick with feeling guilty so that she wouldnt be suspected, and when he was "executed", she knew he would survive because of the Hulk serum. I wouldnt be surprised if she was sleeping with Hank too, or maybe she did when she and bruce were in a rough spot. Jennifer Ross would be a powerful ally for Loki too, she is a PR manager working for SHIELD, she can control the media to make Thor look crazy. Maybe thats exactly what she did.
Imagine two Ultron-level androids, and the Hulk, and then possibly Thor (if they freed him to fight Captain America) working together, They could beat the Ultimates a thousand times over... And utilize the Triskelion to apprehend power from all US Government organizations...
That'd be one heck of a fight scene.