I've raised our DD1 and DD2 as a stay at home Dad for nearly 4 years now, and DD1 is incredibly "girly", into dressing up, clothes, pink, fairies etc.
I had never forced this on her, never bought her toys that are inherently "for girls" and she doesn't watch stuff like Barbie or Angeline Ballerina or whatever. Most of the kids she played with growing up were boys. Her best friend is our neighbour's son who has two brothers.
She sees her working Mum - who hates the colour pink - for maybe an hour a day before bedtime, and then all day weekends. But they don't sit around talking about Barbies and dressing each other up. Her Mum isn't a pink-and-glitter kind of person.
But the FIRST time DD1 saw a Barbie doll, she practically fell over. I bought her one and she adores it, roleplays with it, continually dresses and undresses her. She likes tea parties with her toys, she loves dressing up as a fairy, she is absolutely obsessed with the makeup aisle at the supermarket even though I, understandably, never go down there.
What explains this? I'm her main role model (she's just like me actually, it's scary) but she is absolutely fascinated by girly things. I think the main explanation is that men and women are different, so girls and boys are too. The toys she likes appeal to her on a fundamental level.
If you really think that toy manufacturers make toys and rely on parents and society forcing them on their kids, I think you're mad. They find out what kids like, and girls tend to favour one type of toy while boys favour another.
I notice huge differences already in the way she plays with other kids in large groups. All the boys tend to group up and exclude the girls, while the girls are happy to play with either gender and she vocally bemoans the fact that her best friend won't play with her when there are boys around, so has to play with other girls.
Why are the boys like this? Have they been socialised to detest girls at this age? I sincerely doubt it. I don't know any of my friends kids who have been told to reject girls as friends and companions. But in my experience they do.
To overlook simple instinct and brain chemistry is to essentially deny that at our core, we are animals. A lot of what we do is down to our genes, our brain chemistry and our instincts. You can rail against society at large, Mattel, sexism etc. all you want. But in my experience, kids will gravitate towards what they like, and there's nothing you can do about it unless you want to obsess about it and raise them like one of those poor "gender neutral" kids that are in for a life of weirdness.
If she's happy, what are you concerned about? OK she prefers "boys" toys. You know where they're kept, right? Go there, pick up toy, purchase. I manage it when DD1 wants a new Hot Wheels car without climbing onto a high horse and screaming about how unfair it is that a shop dares to simplify things.