I inadvertently ruined my best friend's life
How did you do that?
I told her lies about someone else who is her idol and she hasn't trusted anyone since.
If you did something bad to them, you should tell her that it wasn't true, and say sorry.  Learn from this mistake, and you can both move on.
Nah I'm going to cause other people's lives too.
I really hope that you aren't planning on doing this again.  As you said, this wasn't intentional on your part, but you can fix it.  To go around deliberately lying to others is simply cruel, and unacceptable.