Exactly is frustrating
I don't really think you are taking everything into account. There are different kinds of strength, it doesn't have to be just raw power. Sure, she is less tomboyish now but come on! She's basically the acting queen of the world, it's not like she has the same freedom as before. Also, every time Livi falls into one of his murdering moods she stands up to him, calls him on his crap and pretty much tells the freaking king of the world that he's being a big baby. She even did it after she threatened her, man. If that's not badass I don't know what is.
Besides, the weather power cannot be a big factor in the story. Remember the Rain Dukedom (in which any royal can call the rain) is a tiny, poor nation in a middle of nowhere. If they have so much power why haven't they taken over more territory?
I think this change is good, it shows us the growth of the characters, with Nike taking a more intellectual approach and growing into her role as queen and Livi just pretty much growing in general (it needs to happen NOW!).
First few arcs: Bad ass heroine.
Now: helpless girl and dragged on conflicts.
So dry and boring now. :/