Major friendship problem!!!?

Its a long story but I hang around with my two best friends called Sadie and Emily. Sadie is the type of person is fun to play with and I have known her for ages but she does tend to walk off with other people and act like she has completly forgotten me and Emily and she doesn't tell us also when you get into an arduement with her, it is really hard to persuade her to be my friend again when we fall out. Emily on the other hand is honest, kind, genourous, very trustworthy and senstive and when we get into to an arguement she apolligizes straight away then again, she is very opinionated and bitchy at times. Anyway I'll get to the point!!! Sadie and Emily really hate eachother!!! they always have. There has been a recent arguement. Sadie went off to these other girls so it was just me and Emily so Emily said something to sadie that got her annoyed with us. When I apoligised to her, it was hard but we are friends again. Then emily was annoyed with me because I was friends with sadie again and then Emily and I fell out. I appoligised to emily. Now that im friends with both of them again i'm back to square one where they both hate eachother but i'm friends with them both. How can I make them two friends so that sadie will ecept her apoligy because she still really hates Emily.