I feel my friend is pulling away and i don't know how to react

So i know this friend since 7th grade (2020) we've been goo friends ever since along with our other friend let's call her maya The three of us met in 7th grade and were close till now

Now maya's bd is this friday so we though of throwing her a birthday surprise at school. I was talking to my friend let's call her rue about the cake and stuff and she mentionned she was not coming i was like why she said she feels her and maya aren't like they used to be

Maya isn't in our class this year and with sm studying we have we don't meet her that much but we definitely do talk to each other joke and stuff and maya herself didn't show any symptoms about her and rue's relationship changing so i told rue maybe she's over thinking it a'd she said that's her problem she doesn't think wisely but still she said she's not coming

Now i'm scared that she's pulling away from everybody and it'll come to a time when i'm next and ​i don't want my trio to grow apart and me becoming a senior next year make this even worst

I feel she's going through something but rue's very secretive she never open up and i always tell her if she needs something or want someone to talk to i'm here and all ears

I don't know what to do i'm not forcing her ofc to attend the birthday party it's her choise and the story isn't about the bd party itself more about rue as a person

I'm sorry if the post is long but i don't have anybody to talk to