How to get a dog to stop barking at a specific person?

My sister recently bough a 6 month year old chihuahua, and I am a 19 year old guy, and every time i seem to walk in the door/room/make eye contact with it, it always barks and growls at me. I have another older chihuahua that is nothing like that. What can I do to get it to stop barking at me?