She ended up quitting because she took a turn for the worst.
The Nightbirde Wikipedia article said:Jane Marczewski [stage name "Nightbirde"] was born in the United States and is from Zanesville, Ohio [and] has had cancer three times. At the time Nightbirde appeared on AGT she was dealing with some cancer in her lungs, spine and liver with an expected 2% chance of survival. After the auditions, Marczewski withdrew from the competition, citing her health worsening and therefore needing to focus on her battle with cancer.
--Patrick