I'm angry, upset, and pissed off at my 'friend' and my ex.
Sounds stressful. Why are you upset with your friend?
She's not a friend, she's a liar and a cheat
It's okay to be upset if a friend has betrayed you. You should take sometime to reflect on the problem and talk to your friend about how you feel. Thinking about the problem first will give you valid points to address and will help the person to see where they went wrong.
It's okay for me to be angry at them and do things like this.
You certainly are allowed to feel all of these emotions when you are wronged. It is quite healthy to express it instead of bottling them up! How about when you're more calm, you can confront them and try to patch things up?