I’m sticking with my little theory that it’s WW smuggling her way into Regina’s house. Maybe it’ll be like a Pandora’s Box redux sort of thing, Regina opens a box and out poofs WW. Rebecca was apparently shooting with the rest of them, and I just don’t see Regina inviting her into her house a couple of eps after they’re probably gonna be trying to kill each other in a street fight. So WW gets inside Regina’s house some other way. If Regina’s smart, she’s got a protection spell around her house to keep WW out, so WW has to get creative and figure out another way to gain access, so she delivers herself to Regina’s doorstep and is picked up by Regina herself and carried inside.