I’m assuming she needed support from other Hellish denizens to get onto the ship given her lack of wings, though there may be ways she could manage without it, and so wasn’t part of the boarding party at all but was just nearby.
Teleportation, Dimension Doors, Zhalk's Bag of Holding, being petite she could had piggybacked on some Tall, Dark and Handsome Demon ... the list of possibilities is quite long
