The partner in The Thousand-Year Door who can blow away obstacles is Flurrie. She is a wind spirit who joins Mario during the chapter set around the Boggly Woods and the Great Tree, bringing a powerful gust ability to exploration.
Flurrie's overworld skill lets her blow away lightweight objects and reveal hidden paths, items, and areas that Mario cannot access unaided. She also participates in battles as one of Mario's partners, using wind-based attacks and other abilities that complement the party's timed-action combat.
The other options are partners too, but their field abilities are different. Vivian can hide Mario and his companions in shadows, Koops uses his shell to activate distant switches or collect objects, and Goombella provides information by tattling on enemies and locations. Flurrie is therefore the specific partner associated with blowing away obstacles, not merely one of the game's supporting characters.