I'm thinking about writing an inspirational book for teenage girls...?

There are shelves full of such books. What do you think would make yours any different? Well, covering 'abortion' before 'sex' or 'boys' could be different... Jacqueline Wilson has an extraordinary talent for writing short novels targetted at the 11-15 age group, when these issues are constantly swimming round almost every girl's mind, and making them into enjoyable stories which address these issues perfectly for the pubertal female. They probably enjoy them a lot more than the kind of self-help tome you're proposing and as a result, the morals and life experience discussed probably has more effect on the majority of girls that age, she makes it both fun and funny whilst always making a serious point.