I'm 13 and I was dating this guy I really liked and then after about a week we broke up. He did the whole oh it's not you it's me thing (cheap right)and then the next thing I know my so called friend is going out with him! I just couldn't believe it when she said that she was only going out with him because she felt bad. And then the next day I caught her making out with one of her ex's!! What am I supposed to do about this friend??

This is what happens when one is 13. Exclusive relations and "breaking up" are not a good idea; going out as a group is much better with no exclusivity.

What you want to do right now is get to know lots of guys and all their quirks/weirdnesses, so you will be in a good position to end up with a winner when you're an adult.

quirks/weirdnesses

This goes both ways my friend, both ways... :)

OP WG is correct listen to her please. And this girl is not a friend, another way to learn about people is to experience how they are.

Find a new friend. She broke "Chick-Code" rule #1. Do not date a Friends Ex (I'm almost certain this is a Bro-Code Rule also).

--- Ask yourself if you would have done the same thing. Probably not right. . So why let someone do that to you.

Wondergirl is absolutely correct. You, your ex, and your friend are all getting used to these adult-like hormones and emotions. If your friend's actions make you feel betrayed or uncomfortable, then find a new friend. Having an exclusive relationship is most likely going to be confusing and dramatic at your age, and hanging out in large groups of friends is a great way to get to know friends of both genders.

Just stay true to yourself and what your conscience tells you!