My mom is addicted to prescription pain killers and what to do?

For her, nothing: You can do will make her stop, and nagging doesn't help anything - often makes it worse. You can tell her of your love and concern for her, get information on where help is available. In some cases, a formal intervention (very expensive and not covered by insurance) can help people get into treatment. Attend alanon meetings for yourself to deal with your issues about her use.