I sometimes tell my mom that I don't agree with how she feeds the dogs because I don't like the brands or I don't think that the dogs are doing well on them. She then gets all defensive. She can never stand to be wrong. She tells me that all of my information is wrong and the vet told her that the brand she's using is good. I, trying to prove my point, end up getting all "preachy" and kind of disrespectful. I even try to show her sources but she doesn't care. She just walks off in a huff. So all that comes of it is my mom getting all defensive whenever I mention dog food and us just being mad at each other for arguing. How can I explain things (such as what I think about our dog food) without making her all upset?