Almost all the successful developers I know started creating software (or at least wanted to make computers do things that they weren't immediately able to do) at a young age. Even you believe it is an issue (and I don't know why it is necessary that 50% of all developers need to be women), this isn't a problem you can fix by talking to a bunch of adults about how to get a career in IT.
Now, part of a lack of women in IT could have to do with gender stereotyping at a young age, but I do not believe that IT is generally negative towards women any more than HR/marketing is negative towards men.
PRO TIP: If you are told you're a crap developer, it's not because you're a woman, it's because you're a crap developer. If you think you deserve some type of different treatment because of your genitalia, you're part of the problem.