Am I wrong for being pissed at my friend for taking someone else's side?
Why does it bother you if she agreed with someone else?
I have been insulted by her too much and this is the final straw.
I'm sure it's frustrating when you feel like a friend betrayed you, but your friend is probably just doing what they think is right. Being angry at them for having a different opinion than you is wrong. Everyone thinks differently and you should be accepting of that.
I don't care what they think and they don't deserve my respect. I'm going to castrate them.
Although it is hurtful that your friend disagreed with you. Your friend has a right to make a choice that she feels is correct. You should not punish her because she expressed herself.