I am sorry you are struggling.

The issue might be your choice in friends. People and behaviors you describe don’t sound like these people are friends yet you refer to them as friends.

You might be getting too close to people too soon putting them into friendship categories before you even get to know them.

I don’t think you need to start being cold and unfriendly.

I think you just need to be more selective and a bit less trusting. This person who is bullying you... how and when did she become a “friend”?