Hi impossible,
I just wanted to welcome you. You will get excellent advice here at SR.
Being an addict in recovery, I can tell you that before I was ready to commit to my sobriety, I had many moments of clarity where I told my loved ones I needed to stop popping the pills. Usually during times of painful WD , when I didn't have the money to purchase them. Unfortunately, as soon as my rx came through all good intentions flew out of the window.
In my opinion, when dealing with an addict in active addiction., "actions speak louder than words". If your sister is truly ready for recovery she will be "chasing" her recovery with the same momentum that she "chased" her DOC. - begging you to take her to meetings or rehab or probably would have signed up already. Has she done that? If not, I doubt she is truly ready.
That's just something to think about until someone who has been where you are comes along.