A Friendship candlelight is kinda hard to explain. I held a candlelight for friendship once when me and my big had a kind of falling out and I wanted to make things right. So, I put a note in the president's file with the candle and I blew it out during the candlelight to make a public announcement of sorts to my big that I hoped we were still cool and would remain close despite all the crap that went down between us. We both cried and it meant a lot to her that I did that. I hope that helps explain it a little better
You could also do a Friendship candlelight if s a sister was especially good to you and you wanted to thank her (helping you get better if you were sick, etc.). Not sure why they call it Friendhsip if you're sisters, but oh well.