This is a very Japanese thing, ZeN, although it's being rapidly imported to the US in the recent years.
Have you heard of Sailor Moon, Card Captor Sakura, Rayearth, Vision Of Escaflowne, etc., etc...? -- these are all "girl's comics." They have been made into movies, too, and English version DVD's are also available, I believe.
In Japan, comics are big in both boys and girls. As you can imagine, though, the actual titles very rarely cross the gender border. The few exceptions include Rurouni Kenshin, hugely popular in both genders.