Varying visa (same route)

Hi all, my wife applied for a skilled worker dependant visa four weeks ago (biometrics on 30th Oct). We haven’t heard anything back yet, and need to travel next month. Her last visa expired on 6th November so she’s in between visas right now.

Would it be possible to vary her application, on the same route, but selecting priority services this time to get a faster update? I called UKVI a few times to check - I was told conflicting views. Two employees said this would not impact her right to stay / work in the UK, but one employee said that her previous application would be automatically withdrawn making her an overstayer.

We have also checked other immigration websites which say that this is okay to do so a bit confused and worried.

Has anyone done this before, or has anyone faced a similar situation? Thank you!