My frind found out she was pregnant & told us she got drunk when she was out party n & now she says she don't have a clue who the father is.. I found out that she was having sex with a friend of ours and she was NEVER really drunk & that she lied. Idk if I should tell my friend what she did because people telling me that its not my place & to let her found out on her own. What would you do?

What you should do is limited to the type of friendship you have with her. In a nutshell though, it really is none of your business and unless she asks you to help, I would stay out of it. That's a pot that isn't worth stirring.