Bubbles gives the broken door a look, wondering if it was punched through, blasted through, or maybe melted through. She looks back at the vehicle to see if there is a simple entrance to it. (Assuming nothing has changed) She looks into the doorway (expecting a stairwell). With one last look around, she floats above the ground and starts to fly quietly down the stairwell, hugging the wall so she is not seen immediately if they left a rearguard behind on the stairs. (so, also not top speed)