My family recently adopted a tiny dog. She was very shy at first but warmed up to us fairly quickly. She is also getting better at being around other people and dogs. We don't know her breed because she was a rescue. The vets saw she's around 3 years old and is some sort of terrier mix. Whenever she gets really happy or excited she goes under the couch. And then she will come out and then back under a few times and eventually just stay's there. She will also nip at you and growel if you try to touch her when she's under it. She is usually very mellow but once in a while will get excited. She also refuses to play with her toys if someone is watching her. Does anyone know why she does this?