I think my best friend is making my depression worse.
Why do you think your friend is doing that to you?
She has been a terrible friend lately, I'm not sure if she really cares about me anymore.
That may be true, but you should ask a professional what they think of your friend making your depression worse. It could be something unrelated and you might not know that by only accusing your friend.
I'm going to tell everyone my friend is the problem but I think they'll recommend professional help.
If you think that your other friends will all agree about professional help, then that should be your first step.  Before you have a full understanding of what is happening, I don't think you should accuse your friend or tell other people about them.  It might not be fair to do so.