Sounds to me that they get along like my two boys. I have a 6 year old male golden retriever, and just adopted a 1.5 year old basenji mix. The boys get along great most of the time but every once in a while my golden gets "snarkey" as you put it but it is only his way of putting Taz in his place, and telling him to stop doing whatever it is he is doing. It is never a all out fight. Imho that's all it sounds like. She is the adult and sometimes puppies bite too hard and surrogate mommy has to put her in her place. I have been around dog's all my life, and when it comes to dogs, if they are playing together most of the time, and she is only getting snarkey sometimes, I wouldn't worry too much. I agree you should feed them separately, treats are OK together unless your adult dog is possessive over treats. My golden is food and treat possessive so I have to do it all separately except cookies. If they have pigs ears they are separated because Levi will steal Taz's because he always finishes first, and Taz is a lot slower at eating his. Taz will chew his in my lap because he knows I won't let Levi steal his treat, lol.
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