But since Vanny has no body to return to (since Delilah destroyed it), Delilah just let's Vanny have control whenever the moment is fitting, or whenever she doesn't feel like being in control, cause the other host can rest, while the other is in control

Well to start, when Vanny originally occupies Delilah's body, she has the more dominant control due to the Solver being an admin kinda thingie, and being new to Delilah's body so she can't residt it as much, but overtime, she adapts to it and can get control back if she wants

Vanny was a worker drone who had the solver (she didn't know), and Delilah was a experimental drone made by a separate drone (Not Cyn), who had eaten Vanny's core, and Vanny's solver partially took over Delilah's Body, so they're forced to share a body as a result. (They switch between eachother)