Except she didn't get fired. She completed her run on Mando, ie her contract was over, and they just didn't continue on with the character in the Star Wars universe, ie she wasn't given a renewed contract for the character. Disney is under no obligation to continue on with her or the character, no matter what she said on Twitter. Now maybe they made that decision based on what was said, but that is their right, just as its her right to say what she said. But given the fact she wasn't fired, and they just didn't renew her contract, I doubt she has any case.