Was I in the wrong?!?!?

Hello ladies. So my boyfriends brother is a complete dick and lies to his girlfriend all the time. Well she came to me and asked me about some of the things he's been lying about. (If he's been smoking weed and why he can't get a job) and I told her the truth. That he smokes all the time and he can't get a job because he can't pass a drug test. I felt if it was my boyfriend I would want to know the truth! But after I told her she went to him and told him everything I said and decided not to believe me and my boyfriend who told her the same thing😑 I'm so incredibly pissed that she did that when all I was doing was trying to help her. Am I in the wrong for being pissed?