I was definitely like that as a girl.
I didn't want to be talked to and I felt bad about myself.
A lot of it for me came from pressure at school to look and act a certain way. This is when kids get obsessed with how they look, they start liking boys, and they start comparing themselves to others.
It is even easier now with social media to get caught up in it.
They also start going through hormonal changes and having periods, which can really throw them off without knowing it.
What I recommend is I would spend more time with her: getting to know her as the developing adult/woman. Letting her know you know what it's like and that you are there for her if she needs someone to talk to.
I wouldn't force her to talk to you about what's going on, but developing that trust and understanding will really help in this situation.
Additionally, finding out what her hobbies are and doing them with her is great too. I know I wanted to seem independent, but I definitely shied away from things I thought of trying because I didn't want to go alone or was too afraid to ask a new friend.
Let me know if this helps!