Chloe is the deceased wife of Buck Cluck and the deceased mother of Chicken Little. It's unknown how or when she died. Since it was never mentioned at all. She is mentioned throughout the film by her husband, her son and his friends despite being deceased.
When Buck Cluck comes home from picking his son up from detention at the elementary school, she is briefly seen in a family photo, while Buck Cluck is saying "Oh, Chloe, if only you were here... you'd know what to do".
Her son, Chicken Little bears a striking similarity to her in appearance. He has her eyes, eyebrows and feather color.
She could have died fairly recently prior to the movie, as they mentioned her a lot.