What should I do? I feel bad for totally messing my friends' lives up.
I'm sorry about your situation. Are you sure you're the one that messed things up?
Yes, when I told them to stop their relationship; they got closer.
It sounds like maybe you got a little too involved in this person's life. Next time you should try to stay away from their relationship with their significant other.
I should let my friends have a chance to know each other
It's good that you recognize that you shouldn't try to negatively influence the lives of others. If you want to make the situation better, you can always come clean to your friends about your interference. This will allow everyone to move forward.