Help me out

Well... First That friend who is pulling away one of your friends is totally wrong for doing that.First Get That person Who IS Mean and look her in the eyes and stand up straight and say something like " Stop It, (Your friends Name) Is my Friend! That Is Mean What You Are Doing!Please Stop it!" then confront her. and tell your friend to ignore that person who is Mean
try to be by your friend Alot so that mean person cant get to her. Hope That Helps , Good Luck! :)

If the friend who's being pulled away from you didn't do anything wrong, then I would only be friends with her. If she did, try to get her to apologize to the first one for whatever she did.

First of all, I would pull Friend 1 aside and ask her why she's doing it.
You might wanna ask her if anything is going on that you might need to talk about.
Then, if she says nothing is going on and that she just doesn't like Friend 2, then I would tell her that true friends wouldn't be so selfish to keep a friend to themselves.
If she keeps doing it, stop being friends with Friend 1 and keep by Friend 2's side, staying as strong as you can for the worst.
Things might get ugly between you and Friend 1 if you don't keep by your friends.
Hope that helps. ^^