LOL! You started it with "dyad" - and as I've revisited your story, I see that Grandma named the girl Millie, you didn't say she was named after Granmda Millie. Oops. I spotted a typo too - alon[g]side.
You created a world with so many rich details - the sympathetic wife of the mean uncle, the cousins, and then the two sisters who appear to be in league with the mean cousins. And the way Millie has named so many trees - she's a forest girl all the way!
The door is wide open for Parts 3, 4, 5, and ....