If Rahab disobeyed her coviction from God, did she have faith in God?

If she disobeyed, she certainly still had faith, but not in God. It would be a dead faith in dead idols.

Notice you added "in God" to what James said. This "more or less" approach is your problem. Don't add convoluted fluff.

Faith in God leads to obedience to God. Disobedience is from faith in idols, such as the flesh, the world, or other false god(s).