To answer your specific question, I don't believe anyone knows the true heart of another, except the Lord God and that person. God knows our true hearts and He knows whether or not we belong to Him.
Although I do not agree with Hillary's actions, I would never judge another one in thinking that I would even come close to knowing of another one's personal relationship with Jesus.
In other words, I would never say to anyone that he or she does not know Jesus, because I do not know what's in their heart, but God surely does, and that's what matters.
We can get a little insight when applying the Fruit of the Spirit as you have quoted here, but never enough to go about stating that someone does not know Jesus as Lord and Savior, as only God knows the heart.