She can't Mimic on demand, as it is her passive. And attacking or being attacked drops the mimic, so how on earth would that scenario evolve while laning? What is she doing? Sitting in a bush letting the ADC 2 v 1 so that she can distract them after he's been pushed out of lane by her nonsense?
As a support, she's going to be more like Morgana. She has a root that passes through minions and an Ult that also roots. The only times I really see her being able to use her passive effectively as a Support during the laning phase would be when they both return to lane so long as the ADC is on board with starting a fight instead of CSing. It will give them a moment of confusion to take advantage of. This can also be done with the jungler with a bit of coordination.
Edit:
Actually, it's starting to very much look like she can Mimic on Demand if her Passive is available. Still not sure how well this would translate in the laning phase as you would literally have to lose sight of both of them for that "switcheroo" to be effective.