Because no Christian has ever commited sin.
This article is not representing this as a woman who just sinned like we all do. She’s saying “I know in my heart I am a religious woman, thus it cannot be that I did something bad. Do not feel bad to do the same yourself. It is time those who view abortion as sin need to reevaluate their positions.”
The question is not: whether or not Christians sin.
The question is: whether or not murder is sin.