im not gonna tell you the exact awnser but heres a parragraph that tells you the awnser in 2 sentences
It was partly because it was the next challenge for me as a writer, to imagine the world from a girl's point of view, but mostly it was because I thought that outdoor adventure novels needed to catch up to real life. Outdoor adventure is every bit as appealing to girls as it is to boys. Just look around at who's out there skiing, mountain biking, kayaking, river rafting, climbing-girls are active in every kind of sport. On our own hikes and river trips we see at least as many girls as boys.