Years ago, before my current partner and I got together, he was dating a friend of mine. This "friend" loved to post on Facebook how happy she was in a way that made it seem like she was out to make people jealous. She had it out for me because she saw the guy and I clicked. She'd go out of her way to make me feel bad for still being single in my early twenties.
One day, a mutal friend of ours told us she was exchanging phone numbers with other men at a wedding. I wasted no time in telling my current partner. He kicked her out of his house fo ra day. He always said he should've stayed away from her after that because she did worse years later.
I think I did the right thing in telling him.