Why did the white witch had no real claim to the throne on Narnia?

If you read the first book of Narnia, The Magician's Nephew, you would find out that Jadis, the white witch, was from another land not in Narnia. The main characters go to that land and see that she destroyed it. Because her sister got the throne and not her. But when Polly and Digory, the main characters, went to Narnia, Jadis tagged along. And she wanted power over all of Narnia so she could finally be royal./ She wanted it for the wrong reason, and Aslan knew that. He was the true king of Narnia. He made it himself. But he still treated his people as if they were himself. Jadis treats everyone like servants. She wanted to be the highest of them all. and that is why she didn't have a claim to the throne.