For now, labelling this character mysterious_girl_(kirby_and_the_world_beyond) based on that exact phrasing being used in the marketing, with the full expectation it will be renamed later. Considering she’s called “mysterious girl”, I suspect that it’ll be a while before we get a real name. https://www.nintendo.com/us/store/products/kirby-and-the-world-beyond-switch-2/