My Stepdaughters Mom Is in Prison for Drugs. We Have Her.?

Is it fair of us to not let our daughter talk to her or write her? We did this because is seemed so hard on her. We also have gone to court and are not going to allow visits after she gets out till she complete a 12 month rehab and can live in society for two years drug free and has a job and stable home. Just want opinions if we are doing the right thing by our daughter. We just want to protect her from the pain she went through for 3 years. Drug of choice was meth. the reason we have some many stipulations is because the statistics for getting off are so bad. She has relapsed several times before she went to prison.