Both the house and Mildred are weird. She appears much younger than the age she claims. She says she gets around, perhaps around includes places outside the passage of time like the Cooee or Engris. This would also explain how a house is powered without power lines. The hastily drawn house number on a paper plate, was it just placed to help them find the house?
This itch Mildred has is a power something akin to skwish but totally alien to it and apparently undetectable by it as well. With the odd assemblage of the critters in the trees we have an interesting amalgam of mysteries to solve. Fortunately, none of them seem particularly malevolent, at least not yet.