Can I tell my best friend to distance herself from her other best friend?
Is her other best friend full of trouble?
Yes, her other best friend told me that she doesn't like her.
Trust in friendship is always critical I understand you are just trying to be helpful with your friend, but their relationship Is their business, and we do not have a say to that. I would recommend that you just be the best friend that you can to your friend, and help them whenever they need to without disrupting other friendship that they have.
Nah, I think I'm just going to tell her to distance herself.
You may think that you are helping her, but what happens if your friend gets mad at you for interfering? What if she cuts you out of her life instead? You shouldn't get in between friendships, and should allow your friend to figure things out on her own.