How can I get my niece to undergo alcohol rehab?

Can you answer debbie p’s question about Addiction?:

My teenage niece lives with me, since my sister (her mom) travels abroad. My sister doesn’t know about her daughter’s alcohol addiction, and I don’t know how I’m going to tell her. I want my niece to undergo alcohol rehab, but I haven’t tried talking to her yet. What am I to do?

Free Drug Rehab Program