If you still have to move her, I'd let her go through her dark 12 hours, then switch her to the other room where the dark period has just begun. This gives her 24 hours of darkness, which is much less traumatic than 24 hours of light if done the other way around.
Do not switch in the middle of a cycle. (like at the 6 hour mark) Lights going off-n-on repeatedly will stress 'em.