I like the idea of Diana flying and using the Invisible Jet. I would have it where she could fly plenty fast under her own power, but, should she choose to other galaxies she can summon the Jet (via a telepathic, magical, or technological link) to get there much faster. As a magical creation, she can alter its shape and upgrade it as she sees fit. Steve and her other WW family members can borrow it, but, it should be hers first and foremost.