Demeanour: Outward behaviour. Eg: Her demeanor changed from happy and excited to down and depressed within a second.
Splendour: Magnificent and splendid appearance; grandeur. Eg: The dress still retained a richness and splendor unlike any garment she had worn since that day.
Persona: The aspect of someone's character that is presented to or perceived by others. Eg: the public persona and the private person are two very different people.
Disposition: A person's inherent qualities of mind and character. Eg: He has the disposition of a saint.
Composure: The state or feeling of being calm and in control of oneself. Eg: she was struggling to regain her composure
Deportment: The way a person stands and walks, particularly as an element of etiquette. Eg: poise is directly concerned with good deportment.
Poise: Graceful and elegance.
Temperament: A person's or animal's nature, especially as it permanently affects their behaviour. Eg: she had an artistic temperament.
Nonchalant: (of a person or manner) feeling or appearing casually calm and relaxed; not displaying anxiety, interest, or enthusiasm. Eg: She was talking about my present life in such a nonchalant way and acting as though it wasn't important.