To Speak or Not To Speak

I was having lunch with my best friend today when I brought up a concern of mine...I'm worried that I'm having too much of an impact in my sister's opinion on matters that are important to her. He clearly understood my concern because he was with me the moment this came to my attention. Brian was out with my sister and me, when he decided to make small talk with her and just ask her some simple questions. He stated that he notices that she has a lot of friends and asked if she felt if all of them were "true" friends. She looked at me apprehensively as she answered, "Well, I think some of them are, but Champagne doesn't believe they are." I looked over and told her, it doesn't matter what I think, it's what she thinks that is important. She looked puzzled, and kept looking at me everytime my best friend asks her a question, like there's a wrong and right answer.
This breaks my heart to no ends. I feel like maybe my voicing my opinions around her has caused her to to stop listening to her own heart. That was never my intention. She came to me crying when a friend has treated her badly, and I explained perhaps this person is not a true friend or perhaps the friend did not realize what she did was wrong. People have different ideas of what is right and what is wrong when it comes to how they treat their friends, it's not always going to reflect how my sister treats other people. I had wished to be a good sister that offers sound advice...not someone that beats her opinion into others.