Regan laughed, her whole demeanor changing once they were inside and sitting down. It wasn't necessary, but she preferred having them both seated while she did this, just in case someone fell over. "Of course it wasn't Pietro," she said, and smiled as she took over Lorna's mind.
Inside the landscape of Lorna's mind, Regan found herself in a garden. Untended and overgrown, the foliage warped itself into shapes and shadows--some beautiful, some terrifying. At the center of the garden was a tall spire, with a broken bridge stretching out from a single window at the top, only to end in a sudden drop into the landscape below.
Magneto had discussed with her what he wanted--rework some of her recent memories to make her more trusting of her father and more amiable towards the Brotherhood's ideals--but Regan also had her own ideas of how she wanted to accomplish things.
"Messy," Regan commented, and laid her illusions first of all over the garden, making it brighter; well-tended and peaceful. Then the tower itself, finding Lorna's sharp temper shot like red threads through the stone, and making those threads stronger, fiercer and closer to the surface. That should serve everyone's purpose well.
Finding Lorna's memories of Magneto, she laid a varnish of illusion over them, so that each one seemed warmer, happier. The remembered figure of Magneto became comforting, and completely trustworthy. All of her memories of the Brotherhood were shifted to be more sympathetic. It was an ideal toward which she should strive.
Lastly, Regan tucked in the two pieces she'd put in Pietro's head, as well. First, the desire to trust Regan, no matter what. And also, tucked into a hidden room at the bottom of the tower, left behind an illusion where it wouldn't be found without the right trigger: a compulsion of absolute loyalty to the Red Queen, and the belief that she was part of a group called the Sisterhood, which must supersede all other responsibilities.
Finished, she pulled back out of Lorna's mind, spinning one last illusion to smooth over the missing minutes. "I wanted to tell you that I'm probably going to be leaving," Regan said, as if there had been no pause at all. "I... I'm really going to miss you. And everyone."