If you are mona'd you have been fashionably inspired or feeling beautiful for an indescribable cause. Mona originates from the latin word "pretty" or "hot" or "stylish" etc. Translated to an english term it would be something like "looking good" or "chic". In celebrity terms people who have been mona'd would be : Gok Wan, Victoria Beckham, Stella McCartney, Paris Hilton etc.
Mona can be used as an adjective or a verb.
May also be connected to the Mona- Lisa which could divert the meaning to possibly melancholy or calming.
How Mona! (meaning how stylish or chic)
Ooh she was totally mona'd. (she was inspired fashionably or look-wise)
She thinks she's all mona doesn't she?
She was looking like the mona-lisa.. all unpredictable.