Friend distancing after long friendship

My friend and I have been best friends since 3 years ago. Shes been a great friend, but I feel as though she’s changing. She’s always been very stubborn but only lately I’ve noticed her feeling the need to disagree with everything I say.

Every lunchtime at school, only her and I sit together but she only wants to talk about herself and I feel as though she doesn’t care about many of the things I have to say.

We’re on our school break right now and I got a message from her saying she now is going to hang out with a group of girls from now on. I do have other friends to see at lunch but it just confused me. I don’t know whether it was wrong if her to do so or if I should just accept it and move on. I completely understand that she feels the need to see other people everyday but it was unexpected. As I said, her and I have spent everyday together lately but now she’s saying she wants to be with other people everyday instead.