Am I wrong?

So I'm in Texas visiting my sister. She rarely gets to see her nephew so I've been letting her help out. My son is 4 months old. He's been sleeping alone since 2 months and falling asleep by himself for the past month and a half. I'm proud of that progress because getting there has not been easy. She's been doing things like letting him fall asleep looking at her ipad, holding and rocking him to sleep, and not finishing his bottles. I'm not sure why maybe she thinks I'm overfeeding him. Well today has been hell getting him to sleep. I feel like it has something to do with her throwing him off so I said something. I simply asked her to let him finish his bottles (4 oz) and to put him down drowsy. She gets an attitude, goes to the bathroom and cries, makes a status on facebook. And now she's not talking to me. Shes not the one that will have to deal with this in two days when I'm gone. Was I wrong?