How can I break it to my aunt that her beloved dog is going to end up biting a child?

My aunt and uncle have this dachshund named Lucy and they love her to death especially my uncle. As funny as it sounds he babies that dog to death. Anyway the dog has developed small dog syndrome from all of this babying and is now becoming aggressive. Everytime they get fast food they will give her some of the food and have even bought her a cup of soft serve ice cream before. It barks and growls anytime anyone pulls into her driveway, opens the door, the phone rings, etc. Also my cousin was playing with her yesterday and she started baring her teeth and snarling at him. A family friend was playing around by scooting his shoe close to the dog and it attacked his shoe. He just laughed and thought it was cute. The dog has even bitten me before but my aunt just shrugged it off and tried to make excuses for her behavior. I am afraid it is going to bite one of my little cousins and do some damage. Something needs to be done this dog is out of control. How can I explain to them nicely that this dog needs to be trained before someone gets hurt?