The titles already exist. The excellent clerk at my local comic store made me a long list of american and international series for my daughter to check out and I've been very impressed. Most of them have to be ordered though, and none are prominently displayed.

So it isn't so much that the titles aren't being created, but I think you're right that the demand will affect what is visible on store shelves.

As the parent mentioned, if you go to Japan, you'll see a thriving market for manga that appeals to girls of varying age groups. So, this would lead one to believe that the demand exists now, it's just completely untapped here. (Ignoring possible cultural differences.) Do you know how you create a large comic book market for older girls / women? Get them hooked when they're young on age-appropriate material, treat them well, and you'll create that market.

Consider 'normal' books. Kids (including girls) have a wide variety of age-appropriate books in a large amount of genres to choose from. I don't understand how there could be a demand for these books, and not those same books with added pictures in them.

You're giving the producers and distributors far too much credit.