Prosecutors say Victoria Moreno pushed Josiah Bell Brown into Lake Michigan near Navy Pier back in 2022, and then made no attempt to rescue him.
Moreno's lawyers say she has been diagnosed with depression, anxiety and bipolar disorder.
In February, she was found mentally fit to stand trial.
On Tuesday, a judge granted a request by Moreno's lawyers for their own examination.
SEE ALSO | Aunt accused of pushing 3-year-old nephew into Lake Michigan at Navy Pier pleads not guilty