Alright, so imagine you got the baby and you got her placed in a way that will help her grow into a guaranteed companion role. But how do you make sure she stays the course?
Enter Ms. Flood. If you'll notice, there's a moment at the beginning where it starts with someone yelling about the TARDIS and asking for it to be moved. This is Ms. Flood. I'd like to remind you that the TARDIS has something called a chameleon circuit which causes people to just ignore it unless it's pointed out to them. Even if it was on the sidewalk the way the TARDIS was, people would walk around it without thinking much about it as if they were avoiding a deep puddle or a telephone pole. Ms. Flood saw it unprompted which means that she's familiar.
This is etched in stone in the moment during the mid-credits scene in which the TARDIS finally disappears and the landlord freaks out about it. During this scene, Ms. Flood says, "What, you've never seen a TARDIS before?" before winking at the camera.
Not only is she familiar enough with a TARDIS to be able to see it without her attention being drawn to it but she also knows what it's called.
And, in almost all of her scenes, she is sitting outside the front of her home just watching it intently but with the attitude of someone watching something play out like a movie. Almost all.
There's one scene, however, in which the timeline gets screwed up and the Goblins take Ruby instead. During this timeline the home of her foster parents gets darker, everyone is sadder, and everyone is missing something they don't know is supposed to be there. Even Ms. Flood isn't perched outside her oddly TARDIS-blue-colored door. She was out buying groceries and then seemed to be in an utter state of confusion when she noticed the TARDIS disappearing.
For the sake of theory, this could be two things, which I'm going to tear into on the next page. That's right, this theory has LAYERS, son.