latisha fisher , 35 , allegedly locked herself in a bathroom at 5 boro burger in midtown manhattan monday afternoon with son gavriel ortiz .
when workers at the restaurant gained access to the restroom , they found the 20-month-old boy unconscious and foaming from the mouth .
fisher had previously been diagnosed as paranoid schizophrenic and was called ` poster child ' for alternative sentencing .
she was given probation for 2011 stabbing of her aunt and was found fit to stay in the community last year .
neighbors say she had recently shown signs of strange behavior .