Please help with this friendship problem

Okay so say you were Rachel. Rachel was best friends with Nicole and Sammy. Nicole and Sammy used 2 be best friends too. Now Sammy is getting really annoyed with Nicole, but Nicole is wondering why Sammy won't hang out with her anymore. Sammy feels that they have grown apart, and that who Nicole is now doesn't mesh with her personality, and she doesn't want to be friends with her. She doesn't know how to talk to her, and she doesn't want to tell Nicole to change or she won't be her friend. Rachel is freaking out because these two have been her best friends for as long as she can remember, and doesn't know how to help either of them. Rachel also promised Sammy that she wouldn't tell Nicole that she was annoying Sammy. Please help!!! What should Rachel or Sammy do?!!?!!?!!

P.S. Rachel, Sammy and Nicole are made up names, but this is actually happening!!!

okay well I am not an 'expert' on this but I have had this situation before, try and figure out the reason why they are getting into this fight, and try and get them to talk it out...you might find out that it was over something stupid but as you know...friendships can grow apart, but after fights or situations like this they could also strengthen, but I think that you should find out why nicole is annoying sammy, its obvous that you should talk to sammy about it just to see if she could stop although I am not sure about what is annoying. anyways it could just be a little bad situation that will go away after talking it out with all 3! not just two of you, its more like gossip if you do that. anyways I hope this has helped