Everyone hates me because I upset my cousin by telling her boyfriend exactly what she's like but forgets how she hurt me Years back?

A few years ago I split up with my ex and I was heartbroken- my cousin and my other cousin started talking to my ex and liking the girl he cheated on me with' pictures too! My younger cousin apologised and told him she didn't want to speak to him again.

However, the older one didn't and continued talking to him and following him online etc- she said it wasn't more than friends at the time and that they weren't talking anymore but I had my feelings that wasn't the case, he has said that wasn't the case and she only unfollowed him when she settled down with her new boyfriend. But she told everyone I was lying and just accusing her.

I was then seeing another guy and all of a sudden he got involved with my cousin! I told the guy what had happened with my last boyfriend that me and her were cousins and what she was like.

He told her and she was upset that he and I had been involved and that I told him all the things. As she turned on the crocodile tears all my family hate my despite how much hurt I suffered because of her not that they believed that she did anything vindictive anyway- they think she just stood on my toes.

What can I do?