I’m glad you have said all that to be honest. I believe her too and I don’t know her! but the codeine is so unforgiving and it makes you lie to the people you love the most. Time scales are definitely a good move and I can’t insist enough that if you don’t set out some kind of agenda then she will manipulate the situation with expertise. Anyone I have every spoken to who is addicted to codeine is a master of manipulation I’m afraid. To really break the cycle you need to give her it “all on a plate” ultimatum and timescale for change. I can tell your not in a great place but she’s 20yrs old and easily fixable without a doubt. With the correct support and pressure she will kick it. It would be interesting to know what level she’s at with codeine/others/smoke. I’m sure it’s tough for you and I genuinely feel your pain and opening up to family can be you last stop. Don’t let her take you down though! Your purpose in life is to enjoy what time you have left with minimal pain so take her to task in the most loving but aggressive way you can. Stay strong and focused but don’t trust her until you seen the results. Remember that it’s not your fault.