Whoa, the female ninja was concerned with who JA was, because she expected Travis to be alone:
JA: "Yeah the girl wanted to kill me too."
Detective Flores: "What did she say? What words did you hear, what phrases?"
JA: " 'Who is that? Who is that and I thought he was by himself or alone' or something... and he was like, 'just finish it.' And Travis was screaming the whole time..."
She's pulling this story out of her own capacious... imagination. An imagination that is populated/fueled/fed only by her own experiences and her own insecurities, because she has no capacity for empathy. So she creates an imaginary girl ninja who, in the midst of this grotesque imaginary ninja crime, takes time to be freaked out because Travis is unexpectedly with a female guest... just like she was freaked out by the things she discovered in her own stalking of Travis.
Wow. Just... wow.