Tried exiting the menu and reloading earlier saves (earliest one I had was right after adopting her). No luck, poor Sofie won't be getting any gifts. /Head desk. Now Lucia won't leave Whiterun because she evidently needs to say goodbye to the entire population of Skyrim and their pets.
BWAHAHHAHA! I had that same problem. I went back and forth for like 3-4 in-game days and she still kept saying that "I need to get my things together and say goodbye to everyone...thanks! thanks so much..." crap--as if a preteen girl and, OH YEAH, A DESPERATELY POOR HOMELESS BEGGAR is going to have a ton of friends in a medieval style town...
Sofie does something similar to that, along with about 50,000 other glitchy things related to her finding your house or something, and it's so friggin' irritating and so much work to adopt her that I just swore it off. Even after I had a game with her as one of my kids that was pretty well along, I just went back and restarted from before I adopted her purely out of spite or something.