The mainstream culture around gender is shifting, which is a net positive in many ways, because it means there are gradually fewer assumptions about what "girls like to do" and what "boys like to do." The fewer assumptions there are, the more free people can feel to do explore what they like at a young age with no caveats.
That said, we still live in a very gendered society, which means young children quickly internalize ideas about what girls and boys are like, and for many young girls - this results in a phase where they try to distance themselves from other girls in an attempt to seem cooler.
Sadly, this is usually rooted in the sexist idea that boys are innately more logical, laid-back and fun, while girls are frivolous and dramatic. Obviously, these traits can apply to anyone, but when you're young and impressionable, growing up in a world full of biased messaging, it's easy to internalize the idea that "not being like other girls" is innately good.