My thought was she was dispatched, ordered, to the DOL where she can find and aid the destruction of AntiBiden efforts
Ok, looking into it a little more, she used to work on the secretary of Labor's staff, so she probably reached out to stay somewhere in government with a future.
Whether she jumped or was pushed we won't know. If she jumped, it was probably because despite the title, "Chief of staff" us kind of a crappy job in government. You get to sit at the big kids table, but you are a glorified secretary, nobody comes to you to formulate or develop anything, you're just handling staffing and scheduling and making sure the principal officers get what they want. It's also one that you get pigeonholed into if you are good, you don't often hear of people going from chief of staff to director or leader of some government agency because they weren't leading anything, they were just making things run.
I thought there was some rumor that Psaki was leaving "soon", so maybe the burrowing was her finding a place with a future, but who knows.