|Portrayed by||Meredith Baxter|
|First Appearance||Beautiful Little Fool|
By the time she was twenty-five, Ellen was raising her two daughters by herself, with Lilly's father having been gone for almost as long as Lilly could remember. An alcoholic and also a drug addict, Ellen raised her two daughters on welfare, often leaving them alone for extended periods of time when she was out drinking or looking for male company. During their childhood both Lilly and Christina often had little to eat, save for free cornflakes given out at their school, and as Lilly once put it "whatever was under the heat lamp at 7-Eleven". As a result of her addiction, Ellen often relied on Lilly to go to the store alone, even at night, when she was out of alcohol. One of these trips resulted in Lilly being attacked, leading to a broken jaw which Ellen later attributed to Lilly being a wild child in a conversation with her fourth husband Jackie. This incident was a milestone in Lilly's life, motivating her to eventually become a police officer, though she remained traumatized by it as she clearly displayed when taunted about it by George Marks. As they grew up, it was clear that Ellen favored Christina, who shared some of Ellen's weaknesses, often defending her to Lilly, the more successful of the two sisters. Despite their differences, Ellen and Lilly did form somewhat of a bond, with Lilly having fond memories of her mother reading The Velveteen Rabbit to her many times throughout childhood. This bond caused Lilly to stand by her mother over the years, despite the emotional scars Ellen had caused her throughout her childhood.
It has been alluded to but not explicitly stated that Lilly and Christina do not share the same father. In total, Ellen was married four times over the years, with Lilly being her maid of honor at her last wedding to Jackie. Considering her strained relationship with her mother, Lilly suspected (possibly rightfully) that she was only asked because her sister Christina was on the run from the law and could not be found. Much to Lilly's chagrin, Ellen completely glossed over her past and addictive personality to Jackie, which possibly contributed to him walking out on her during their first year of marriage, when she could no longer hide her demons from him. This led to Ellen going on a large drinking binge that ended with her spending the night in jail and Lilly having to come and bail her out, with Lilly alluding to the fact that this incident is not a first.
Shortly after the break-up of her last marriage, Ellen was diagnosed with liver failure and ordered not to drink, an order which she lost no time in disregarding. Faced with no other option, Lilly moved her mom in with her and took care of her, even uncharacteristically leaving work to make sure her mom ate lunch. Unexpectedly, Ellen Rush passed away when Lilly wasn't home, leading Lilly to feel guilt and even resentment that her mom hadn't attempted contacting her on her cell phone. After Lilly was shot in the line of duty later that day, she had a seemingly near-death experience where she called out to her mom while on the operating table.