The "heartwarming", positive cover is indeed heartwarming and a good message, but is also pretty lame, and unlikely to sell magazines.
I also question whether this is typical shallow/ignorant internet outrage. When I was a kid, Boy'a Life was a Boy Scouts magazine, and had annual themes that appeared every year at the same time. If you looked at the May/June cover, the annual Boy Scout Jamboree issue wouldn't be as "internet offensive".
Should A Girl's Life change the tone of their stories? That's up to the market. As long as their demographic enjoys what they print (which translates to $$$), they'll continue to run it. Should people be outraged by it? If they choose to be, yes. But at the end of the day a consumer is a consumer, and if they want trash they'll get it.
I a few words: the same person performing the same task will perform lower if they are aware of a stereotype that says that their group performs worse at the given task. It is reproduced for white and black, male and female, etc.
Which is really sad, I really hoped we can all agree that your sex does not determine whether you are a good engineer.