This character is a cheerleader.

Cheerleading is a physical activity, sometimes a competitive sport, based on organized routines, usually ranging from one to three minutes, which contain the components of tumbling, dance, jumps, cheers, and stunting to direct spectators of events to cheer on sports teams at games or to participate in competitions.

While cheerleaders are usually students cheering for their school's teams, there are also non-student cheerleaders supporting professional sports clubs and similar.