Deborah “Debbie” Gallagher is the fourth Gallagher sibling. Although she tries to act hard and comes off as a tough girl with a spunky attitude, she is known for being helpful with good intentions and has a caring heart. She's willing to bring her baby brother to school for show and tell when there's no one else to watch him, place a pillow under her father's head when he's passed out on the floor, and collect money for charity year round — only some of which she keeps for herself.
She is one of the only Gallagher children to still be hopeful of Frank eventually behaving like a real dad, even with Frank's continued mishaps. He had inadvertently crushed a replica version of Abraham Lincoln's home made out of popsicle sticks, a school project Debbie was creating, she grabbed a large bag of soap and numerously hits Frank with it after she hears him call it a “piece of shit”. This seems to be the thing that breaks Debbie's thoughts of Frank being a nice wonderful person who just wants a chance, she then realizes he isn't a good father, and is only one when it suits him, Frank was kicked out while Debbie wanted be alone in her room.
In the very beginning of the series Debbie is described by Frank as being “sent from the gods.” However, we soon learn that description is a bit of an exaggeration. Except not by much because she is extremely mature and grounded for her age. So much so that she has trouble relating and socializing with kids in her age group.