I think dreamer is right. If we remember that All is Oneness, we'll see that the dark is as much part of us as the Light. Acceptance is key. It may seem frightening and strange, but it's all for the Greater Good. Things are being healed in your friend...there is no cause for alarm.
I know how it feels to want to do something, so what I would suggest you do is surround the person with Love. Remember what I said in another place about Being.