Disagreement (graded)

I have been in a HUGE disagreement just recently with my sister. She was dating this guy that I didn't practically like. I thought he was playing with her and leading her on and she didn't agree with me. He didn't want to spend time with her or act like he did and when I brought this up to her she was clearly upset. I tried to talk to her about it and talking about their relationship got worse and worse. Our family got involved and my sister had enough and stopped talking to me for about a week. I was only trying to help her and she didn't want my help. He was totally not that into her and she thought he was. It turns out I was right the whole time and she finally realized that I was just trying to help her and were back to the same as we were before. Leason learned by both of us. I have to let her learn her own mistakes and she needs to know a red flag when she see's one.