My Friends hate each other?

Ok. I have these friends Valeria, Britani, Kayleigh, and Darion. I'm going into the 8th grade and I have known Valeria since 6th grade and I GUESS we're best friends. But I have these two friends Britani and Kayleigh that are just amazing. They're considerate and they care about my feelings. Last year we were like the 3 Musketeers. Then theres a girl Darion that is a grade over us and shes another one of my besties. Im really sad that Darion's leaving for high school but I dont really know who I should hang out with next year. these are my choices. I have Valeria who constantly lies to me, steals from me AND my friends, and she never thinks of anyone but herself. Then theres Britani who is really nice, crazy but fun to be around, and Kayleigh who is in the same GirlScout troop as me, and she is really cool. Valeria is an OK girl, but how do i tell her that we've kinda grown apart after being BFFs for 2 years? Should I not say it, but show it? Should I show it by hanging with Kayleigh and Brit? I know this is really long but I needed to get this off my chest for 2 years. I might need to continue this. Im sorry...LOL