Is this a type of bullying and should I be concerned?

I'm new to teaching year sevens and honestly, teacher year ones was easier. There is a group of girls in my class who have been friend scince 2015. One of the girls, from what I see is being excluded now in most activitys, like they will pass notes and not show her, they'll target her in class games and break time games and she'll never be noticed when she is sad. On Monday she came to me for help saying she feels they are gossiping about her, what do I do?