This also applies to boyfriends.
Your friends know you as well as someone can. They have seen you grow, change, learn, they may even have known you your whole life. They have seen you happy, distraught, successful, helpless, disorientated. They have seen you react to new people, new places, new experiences. They have even seen you when you thought no one was looking, when you were lost in your own world, your own thoughts. They know you. Probably better than you think.
True friends don't have vendettas. They don't have ulterior motives. They're your friends, not relatives who perpetually misunderstand you. They care about you. It's as simple as that.
I'm not saying it's easy. I know it isn't. I don't have a magic solution that will stop you going to the wrong person, make your partner and friends get along and smooth out the rough parts.
They're your friends. Trust them.