Everyone is talking about it so here is what i think happned to her.
My guess is that she wasn't taking her medication properly and that she was told by a hallucination to hide somewhere (like the water tank)
Her Family said that she would often see things and its common that you would hear voices and they tell you violent or concerning things. we can see in the elevator that she is interacting with what I believe is a hallucination or a voice in her head.
Her being naked was either her being told by her hallucination or done on her own will by trying to stay afloat.
She was on medication for her Bipolar Disorder and right next to skid row so its possible that she got drugs from there and was mixing the 2 but I don't really think she took anything else expect for her prescribed medication.