No, it's never too late for someone to change—although the older we get the harder it becomes. But God still can change someone's attitude if the person is willing, regardless of their age. Jesus said, "With man this is impossible, but not with God; all things are possible with God" (Mark 10:27).
I have often pointed out in this column that racism is a sin—and the first step your aunt needs to take is to face this truth. God made us all, regardless of our ethnic background or race, and He loves us all equally. Should those of us who claim to follow Christ love others any less than He does? Remember, by His death on the cross Jesus "purchased men for God from every tribe and language and people and nation" (Revelation 5:9).
But racism is also wrong because it has its roots in pride—believing we are better than other people are. But pride is a very serious and dangerous sin in the eyes of God. The Bible warns, "The Lord detests all the proud of heart. Be sure of this: They will not go unpunished" (Proverbs 16:5).
Pray for your aunt, and ask God also to give you an opportunity to confront her with your concerns. She may not even be aware how deep her prejudice is; if she grew up this way, she may never have examined it. Above all, encourage her to open her heart afresh to Christ and His transforming love.