Actually, she said it more than once– and then lied about using it.
She told a talk show host she had only ever used that word one time in 1986 after having been robbed at gunpoint. However, she admitted under oath during a deposition (involving a former employee of her network who was suing for race and sex based discrimination) that she had also used the word since then, including while planning her brother’s 2007 wedding. She originally had in mind a “plantation-style” wedding and wanted to hire African-American men to serve the food. This idea, thankfully, was rejected.