When people get into an argument or end a friendship or some sort of relationship whether it be with someone professional or a boyfriend/girlfriend, people SHOULD tell each other what they think. What they SHOULDN'T do is tell everyone else except you what they think. They also shouldn't tell people your side of the story unless you are there to defend yourself or state facts. Actually, scratch that. They shouldn't tell people anything that has to do with a situation between you two unless people ask. If people do ask, spreading lies and negative comments about that person and the situation is not the answer. If you're going to hurt me you could at least keep it between me and you, not me, you, and all of our friends. It's as simple as that but clearly some people learn faster than others.
If you have something to say, say it. Not over text, not to other people, to me and me only to my face. This is a very valuable lesson and the first step to handling a situation in an adult, professional matter. If you're going to hurt someone that went out of their way to support you, stay loyal to you, and genuinely care about you, the least you could do is talk to them in person. You listen to my side, I listen to yours and that's the end of that. If someone says you hurt them, you don't get to decide that you didn't.
The best thing to do is move on. Move away from that person's negativity. Learn from it and forgive but do not forget. Focus on yourself and succeed in everything you do. It kills someone to know you're doing amazing things when you aren't under their control. It makes them look bad without you even trying. Surround yourself with the people who bring out the best in you and teach you how to be a better person. Learn from the hurt and never let anyone treat you like that again. If someone wants to try to turn people against you, that just looks bad on them. Be the bigger person and you end up winning in the end. Take your hurt and anger out in a productive way and do not get down to their level. Karma may take a while to work its magic, but it always comes back.