>>328224963
Are they making things up, saying some embarrassing fact they learned about you or are simply narrating a negative experience that actually happened between you two? If they're making shit up, prove them wrong. If they are telling some embarrassing secret of yours, you're more likely to be considered a victim by your friends. If you did them wrong and they are telling what happened, you get what you deserve.

>How do you avoid people like this?
Avoid the known shitstirrers like the plague. Only trust the people who trust you. Trade bits of trust at a time.

>How do you fix this?
If you're actually a victim, explain the situation to people you trust. Unless the person spreading rumors is literally satan, they will probably stop if you ask them to. If they don't see the effects their bad actions have on you, it's unlikely they will feel guilt.
If you did something wrong to the person telling on you however, you'd better apologize and try and make things right with them.