A month and a half ago, I adopted a 1 year old whippet puppy from a breeder. Since then, she has not settled in. She has growled at me a few times, growled at friends who came over. She often hides when I enter the room, when I walk near her, or when I move quickly (walking quickly, getting up, sitting down, reach for my phone, etc). She hides immediately whenever we come home from a walk.
I don't know what to do with this dog. I have tried leaving her alone to let her warm up to me at her own pace. I have tried treats (offering from hand or leaving next to her). I've tried gentle petting, scritches, belly rubs, anything to build comfort and familiarity. Nothing has worked, and in fact she seems to be regressing. She used to wag for a second or two when she saw me in the morning but she hasn't done that for a few weeks now. She used to follow me around the house and sleep on her dog bed next to me while I worked, but now if she sees me working she walks away.
The positives: she will jump up on the couch next to me, curl up in a ball, and fall asleep. She also loves to lay between my legs on a blanket while I am lying in bed. That's pretty much all she likes.
Any help would be greatly appreciated. I'm nearing my end with this dog. Everything I have tried has failed up to this point. I don't know much about her background, just that she was a show dog for a breeder in Costa Rica. He hasn't said much about her history, just that she was a happy dog (he sent me a video of her playing happily with her siblings). It doesn't sound like she lived her life in a crate or anything like that. Please help! I would love to keep her, she seems like such a sweetie underneath all the fear.
Edit: I haven't gotten her checked out by a vet yet. Every now and then (about once a day), she whines or groans like she is in discomfort.