According to the article Rice:
"questioned the word “Christian”, asking when a word becomes “unusable … so burdened with history and horror that it cannot be evoked without destructive controversy”. The next day she concluded that she was “out” and announced her refusal to be anti-gay, anti-feminist, anti-artificial birth control, anti-Democrat, anti-secular humanism, anti-science, and anti-life in the name of Christ.
“In the name of Christ, I quit Christianity and being Christian,” she concluded Wednesday.
From the rest of the article it becomes clear that this isn't about giving up on faith. It is about someone struggling with everything about Christianity that fails to reflect Christ. A struggle we ought all to take seriously. This is why some have looked for an alternative word or phrase, red letter Christians for example.
Perhaps we need to reimagine the meaning of "Christianity", to think about how we can redeem the term and rescue it from all that isn't Christ.