From an addiction standpoint this is what I have heard and believe: The day or time from we start abusing drugs and alcohol its like our maturity just stops in its tracks- it freezes. Its like the substance abuse halts our ability to grow and mature and move forward. When we get sober theoretically we are supposed to resume maturing and growing. I believe that is because we are no longer hiding behind our addictions. In theory, your sister would have gotten sober and done some serious self reflection and changing and be able to make strides covering the ground she missed when she was using. But some people do not do this. How did she get sober? Did she go to rehab or use a 12 step program or just stop the drugs? Self reflection is a must when you stop using drugs and alcohol. Without that you are the same addict just without using the substance.