Question: how to say no to your best friend?
Answer:  Don't wait until you're fed up. ... 
 Don't feel guilty. ... 
 If your friend can't accept NO for an answer, recognize it as her problem not yours. ... 
 Carefully consider why you've decided to say NO. ... 
 Try to say NO as graciously as you can. ... 
 When you're both relaxed, talk about limits and boundaries in friendships.