Who Liz is trying to protect is debaitable.
I seriously doubt that she is tryng to protect Sam, she maybe trying to protect Lucky, but it's not from falling back into drugs.
I mostly think that she just doesn't want to have to admit to Lucky (or anyone else) that she has done something wrong. She does not want everybody to know that she is no better than anyone else. Everyone one will know that she slept with another man 5 minutes after she ended her marriage and has been lying about it ever since, plus is tricking Lucky into thinking that the baby is his. Once the truth is out - There goes her reputation!
You know how it goes once the lies start you have to keep covering with bigger lies! I just wonder if she is a big enough liar to try to deny it when the truth comes out or if she will turn on the3 water works and try to somehow pass the blame on to Lukcy and his drug dependency for her ONS with Jason and all her lies!