How do you feel about "friends" that 2 face you! Whats your opinion?

What if you had a friend that talked smacked about someone behind their back an telling you how much they hate that person but then they go off talking smack about them behind their backs, act all 2 faced. Do you believe that they're probably talking smack about you as well? Bc I know this girl name Mel, she told me how much she hated this Arica girl but then I find out on facebook she's talking to her. Do you think she can be trust or do you think I should get rid of this mel chick bc this Arica girl doesn't like me, same with the rest of her friends. Whats your opinion?