I’m familiar with the TSP as I’m also a federal employee. I’m not at all familiar with the rollover process and the benefits of private sector 401k vs TSP since I have only ever dealt with the TSP.

Thanks for the feedback, my assumption was moving into the TSP was the best move. And I don't think she'll be leaving federal service until retirement; she will have much more room for growth at her new job and it's hard to argue with a pension + TSP.