No, it's not a typo. The term grrl was one of the first online jargon references in NetLingo.com. She is a female Internet user (as in a girl, even though she may be a woman) who uses zines, vanity pages, and/or blogs to express herself.
The term originally comes from feminists and female punk rockers =:-0 who like to toy with the status quo...instead of spelling "girl" the traditional way, they started spelling it online with two r's. The spelling became mainstream early on when the development of a women's technology support group called Webgrrls, gained popularity in 2000. From hereon, it simply refers to a girl (and a woman) who spends a lot of time online 0*-)