First of all I know here in Texas Title 1 makes it so that PE is now all coed..for all of the years in school..
The next thing is that as other moms have said, this still falls in the normal part of being a teen girl.
I also agree to look at what her actual interest are.
Our daughter was always way more mature than a lot of her peers. She had a few friends, I would not say any best friends until she got to College.
She just could see the games other played in middle and high school and was not into playing those games.
She began to find others that had her "nerdy interests". At the time she was into anime, she loved art and she decided to try Rowing.
It seemed there were others with these interest so she did not feel all alone.
Ar school when the dances were going to take place, she volunteered to make the signs advertising. She volunteered to help sell the glow necklaces and the snacks.. This way she was there, but did not have to dance.
She spoke with the librarian about allowing the kids to put together puzzles, before school and during lunch time. They still do this at that middle school.
The Art teacher realized there were a group of kids that really enjoyed art, so he started and art club. We even organized a trip to see the Monet exhibit in Houston. Again, these tended to be "her people"..
So help your daughter realize that she may feel different then others, but in reality there are other students like her, she just has not found them. Offer to send her to some classes this summer or for her to join sports team, volunteer group. Let her take a Red Cross baby sitting course so she can begin babysitting. These will be accomplishments of her own. She will not seek the approval of other kids so much.
Do keep an eye on her and if she begins to change her attitude about school, homework or at home, speak with her and see if it something more serious.
PMS is real and even if she has not started menstruating. the symptoms still appear. and the more females in your home.. the more magnified it can seem..