It seems like Lewis has finally graduated and earned her doctorate, presumably, in political science at Culver University. Again, why S.W.O.R.D. would need someone with experience in political science is still a mystery, but it could have to do with the environment that Wanda has created in her literal bubble.
It could be that Lewis is acting as a consultant for agents who attempt to enter WestView and how to interact with the people in it, especially Wanda and Vision.
In an enormous media kit release for WandaVision, a production brief was released with it, giving a ton of behind-the-scene information for WandaVision. This includes backstory on some characters like Jimmy Woo and Darcy Lewis:
“She’s gone on to become Dr. Darcy Lewis now…So, she’s a real expert in her field.”
Lewis is joined by Jimmy Woo who, together, “have a mystery to solve,” with Schaeffer adding that “They have so many questions and no answers.”