This is a kind of girl who has a random sense of humour, usually a lot of friends and is very flirtatious. She is the type who will snatch your boyfriend right up from under your nose and then act like she did nothing wrong. Johanne's are usually the type to be involved in dance or some other kind of sport related thing, and are usually considered to be quite pretty. Other girls can be quite bitter towards Johanne's however, because of their reputation as being a man eater and are sometimes unfaithful. They are goofy but somehow womanly at the same time.
Uhg, that girl my boyfriend is dating now is a textbook case of a Johanne.