It is no trouble at all.

[ He turns to the side and waves a hand through empty air, but pauses before it finishes its arc to glance over at her. ]

You will see a spinning blue light on the ground as I cast the spell. Unfortunately, it closes after the caster steps through, so I must ask you to go first. Is that alright?

[ Cuz this spell totally has a limited lifespan, and he doesn't want to spend it convincing her that it's safe to step through. ]