I have an 8 week old labradoodle pup and I am beginning to train her. She does great with all the basic commands, but for some reason whenever I try to teach her to come she gets very aggressive. I squat down and beckon her to come, and she will first get defensive and then come but do it while barking and growling - and once she gets to me she nips at my hands. It's difficult because she is technically coming, and I want to reward her, but I cannot reward her for her aggressive little temper-tantrum getting here. I am not using a harsh voice, I don't understand why she is reacting this way. I'm thinking that maybe she reacts this way under frustration and that I am not teaching her correctly? Or is this a puppy trying to be dominant? Any thoughts/advice?