Hello, I need some advice. I have a 6 year old female lab/greatdane mix. I have been married to my wife for nearly 2 years and things have been going well between her and the dog. For some reason lately every time my wife tries to get Lola to go outside Lola has been growling deeply at her. My wife has not and is not abusive to her in anyway and feeds her nearly every night. What could be causing Lola to do this?