Take personal advice

Some years ago, I realized that a friend of mine was perceived in the wrong way by the environment. We were on vacation together and I heard and understood what people said about us and especially how she was perceived (by her look; hairstyle and clothes). I frankly told her, and I gave her some advice. Was she happy about my advice?
No, she wasn't. Of course not. She took it as an insult. Of course she was right to be insulted by the prejudices of the environment, but she was also insulted by me, for telling her.

Looking back, what can I learn from this? People don't always want to know the truth, and it is risky to tell a friend something negative. But I guess I am also like her. I tend to get insulted too.
When people tell me how they perceive me or something I do or say, I should be grateful and listen carefully. Not be insulted.