It's not a constitutional requirement
Nowhere in the Constitution is it required that a Supreme Court justice be a judge. They don't even have to be a lawyer. In US history, about 38% of all Supreme Court justices had no prior judicial experience. Some of them turned out pretty good, such as Earl Warren and Rehnquist. Why levy an extra-constitional requirement for a job reviewing the constitution?
I don't know her from Eve. I don't know if she'd be conservative or liberal. I do know that she has been nominated and deserves a fair hearing in the Senate. Regardless of whether she gets approved or not, basic descency says she deserves her opportunity to defend herself in the hearings.