What do I do?

Background:
One of my best friend forever Fiona has this guy friend who absolutely is in love with her and he asked her out, she said no, and now he's been trying to get closer to her and eventually convince her that he is an awesome guy and go out with him.
He has got her around her finger. She is not a very smart girl when it comes to guys and she gets confused easily. When ever Cloe and I say something and might be a sick joke that is TOTALLY obvious, she won't get it. Which is perfectly fine by the way, but she doesn't understand people very well. She can't read your face to see if your happy or if you're faking it. Or if your sad or just bored.
So I really do NOT like Caleb (the guy friend of Fiona). We always fight and never agree on anything. He always wants to get into my business and know everything that goes on with me and Fiona so she "doesn't get hurt." He thinks I'm a bad friend because I can't agree with him. But me and Fiona are close. Really close.

Today:
So then today she was at a lunch with the principal outside of school because she was a student of the month.
Me and Autumn were in the cafeteria and I saw Caleb at his normal lunch table and i held my fingers up in a 'gun' shape you know, and went POW. (It was an inside joke from 7th grade just so you know. I'm not the violent type. :) lol). Then we looked at some cute guy in the lunch room and looked back and Caleb was gone. I was like "WOW I MADE EM DISAPPEAR."
Autumn told Fiona later and she laughed.

Then Fiona told Caleb and Caleb got mad because he takes things seriously! It's really dumb.

But I really don't care that he knows the story. Really, it's dumb. But the thing that gets me is that it was just a joke. I tell her everything. Like why I don't like him and stuff and stupid stuff about him that gets me upset.
She's told him everything. I've gossiped a little bit about him and how I want him to move away.
He causes 75% of the shit i have to go through.
And she tells him everything I say! I don't want him to know somethings.
It's not just about him, but about my personal life. Like inside jokes, or that my cat died, or dumb stuff. I'm not even close to him. I hate him so much.

When ever I used to talk to him, he'd only talk about Fiona and how she had "sparkling eyes" and how wonderful she was. It got tiring after a while and he said some stupid stuff that was really cheezy. She thought he was really stupid, but she keeps giving him false hope.

He thinks she loves him like he loves her. But she's too blind to see that they are not just friends in his eyes.
All my secrets are out. He also prints out all my emails where I say something secret to him, and he tells his friends.

I never email him anymore. He's blocked on my IM.

I'm going to talk to her and tell her some things need to remain a secret. Thats why they call it a secret...