Was I Entirely Wrong?

Me and a girl built a friendship, we hit it off quite easily because we had A LOT in common. She even knew my ex because she went to school with him “but they never talked”. Fast forward months into our new found friendship she starts talking to this guy who I’m friends with. He tells me he’s not interested in her fr so I tell him to let her down easily instead of leading her on. So he does this and tells her how he feels, she offers him sex, etc. He blocks her and I’m the one she cries to about it, so I explain things to her, like you can’t believe sex will make a guy like you. Another month later she post a picture of me and my ex she claimed to never talk to saw it and called me. He tells me the whole story behind them, how she had been sending him nudes and she was one of the girls he cheated on me with. He sent me screenshots of him telling her about me and her still proceeding to throw herself at him. So I just silently distance myself from the friendship. I stop talking to her and answering her calls because I was hurt, she lied to me with no remorse, knowing how much he hurt me and for me to have to learn this information from him instead of her who I thought was my friend only made the hurt worse.

So me and the guy friend become closer. Back in January (3 months after me and the girl stop talking) he sends me a long message about his feelings for me and I honestly felt the same about him. He was someone I could go to about anything and not feel any judgement. He supported me through a lot of things so we start dating.

The girl recently found out and started going around calling me a hoe who stole her man to a bunch of people. Bashing me on social media, etc.

I just want to know am I wrong? Should I not have gotten into a relationship with him? Honestly what’s your opinion on this situation? I don’t know what to do at this point.

We’re grown, at least everyone else is. She’s 18 in the 11th grade. Problem is the crap she’s putting on social media is effecting my job tho. I work in a high school, as a secretary and the principal brought up to me because students were showing it around.