My sister is acting strange

I dont really know where to put this but the mental health support group seems fitting. My entire family each struggles with our own personal mental health, some a bit more than others. Im the oldest of 4 girls. The youngest is 6 years old(im 21 with a baby on the way) and in the last couple months she has been acting interesting to say the least. Now bare with me please as we are really concerned. She stayed almost a week out of town with her grandmother and step aunt who has a lot of people living there. Strange people. She came back almost like something had happened but we have made efforts to ask and she hasnt said. Since then shes been acting exactly like a cat. She thinks shes a cat, shes been biting and scratching(she drew blood on my leg) and she meows or growls too. When she wakes up she stretches and moves around like shes an animal, sticks out her tongue and even does this when she doesnt think we are looking. My mom has tried to figure it out and just assumed it was a phase but its been causing some real problems with her behavior. Is this even a real thing? Can trauma create her behavior in a way that she thinks acting like her favorite animal is her safe place? Is this a phase or cause for concern?