Bear with me guys... this might be long.
So Sam is just shy of 6 months... and I'm at my wit's end with her. She was very shy as a new puppy and later turned out to be quite energetic and nippy. No matter how hard I tried, I could not teach her bite inhibition - no amount of yipping or noise or ignoring or stuffing something in her mouth would help (including leaving the room, standing still, etc). She loves to play fight, which I do not allow. Now that is she 50 lbs of trouble, this is getting dangerous.
I started training her as soon as I got her, and she caught on to everything really quickly. I have socialized her (and continue to) as best I could, with people and dogs. Dogs, great, people, huge fail. She is territorial and extremely prey driven. I have never been able to tire her out with any amount of exercise - both physical or mental.
Backtracking - in the mornings, she is quite cuddly and lovable. When I'm at work, my parents look after her, and she is the same with them - cuddly and loveable. When I get home from work, she is wiggly and whimpers and has never acted so excited to see anyone (this includes all people she knows well). As a side note, with my mentally challenged brother, she has never nipped him, only tries to lick him to death. But towards the evening, something changes.
At first I attributed it to teething so I have tried different tactics. Exercise, flirt pole, ball chasing, training, walking, jogging, walking while training, putting her in time outs outside, putting her in her kennel, keeping her on a leash that is tied to me. I think I've actually tried everything other than hitting her or tethering her (actually, there's probably a lot of negative physical things I haven't tried). If I put her in her kennel or outside, she doesn't sleep so its not from overexhaustion either.
The other day she growled and bit me when I was trying to move her and her treat (this is the third time she did it and I only did it because it was absolutely necessary - I tried removing her, not the treat). She does not exhibit food guarding or food aggression with her kibble, just her treats on this third occasion. I know to leave her alone when she's eating, and I have never teased her with treats or have tried to take them away, so I'm not sure where this treat aggression stems from.
Tonight after a long walk and some supper, she was acting up, so I put her outside where she seemed to have settled. I went to take the garbage out, and she ran after me and bit me really hard - not landsharking which is usually a quick nip. This was a solid bite through my pants that took skin and left a bruise right away. She then started lunging at me and growling and nipping at me.
I'm at a loss. I have no idea what to do. I'm not sure if she'll outgrow it. I have wondered if its teething pain but her back molars are in and have been for a couple of weeks.
I am up in northern British Columbia so have found a nearby trainer/breeder with proper training, but haven't met her yet so am not sure how much she'll be able to help. Other than that I'm not sure of any nearby resources. The downside to living in the middle of nowhere.
I'm sure I'll get lots of suggestions of things I've covered but haven't remembered to write here... if so I'll let you know
I have an animal science degree (I went to UBC Vancouver - based on how much I loved my last dog), and have never had problems with any of our previous dogs and can even handle some pretty tough horses. So I know my toughness and my gentleness is there, but I cannot seem to get through to my dog when she's like this. I feel like my only options are to a) give her up to a rescue or b) wait until she does something really awful and have to put her down. Neither of those appeal to me. She has lunged at a care aide at work while I was visiting, and she has bit/nipped a child visiting her at the kennel (I have not taken her back to the kennel since then as I'm not sure why a strange child was allowed to pet her).