My complicated friendship

I treasure my friendship alot, just like everyone else. We can't LIVE or even SURVIVE with friends. So, instead of telling the loooooooooooooong story, I decided to cut it short:

My friends and I formed a group of 5 BFFs, but I have 1 special BFF in the group. But 1 of them always hang out with another friend, and always interrupts when I'm talking. So one day, we had to form a Social Studies group, so I pick my usual BFF gang. But that certain one's 'friend', will come too. :( She will find excuses so that she can play with my friend, and this member of my BFFs is planning those excuses too! So I ignored them, told them how I felt (NICELY), explain all this to them, but nothing worked!! They still played with each other.. What should I do? I don't want to lose my friend..!!

Tell her it's not necessary to make excuses to play with your friend, just invite her to join in! There's no reason why your group of five has to be exclusive- add a 6th member!

But when I invite her to join in, she would only play with that friend of mine. She often interrupt me, and the other 2 also hate her for the same reason. The other one, though, is right in the middle. She's friends with that 6th girl, but also kinda hate her.