Ellis is the mother of Meredith Grey. When first introduced to Ellis, she was suffering from Alzheimer's and resided at the Roseridge Home for Extended Care. Her case was advanced, and she most often thought she was still completing her residency. As a result, she seldom recognised her daughter, but delighted in visits from Richard Webber. When Richard decided to salvage his marriage to Adele Webber, Meredith was forced to break the news to Ellis that he would not be visiting any more, which caused her to relive their initial break-up.
She briefly became lucid and the last thing she remebered was her fight with Meredith about going to medical school. On discovery she had Alzheimer's she was distraught and had a cardiac episode, leading to her being admitted to Seattle Grace Hospital. While she was there, she met Cristina Yang and Derek Shepherd, showing how perceptive she really is, working out the close relationship with Cristina and Meredith and working out Derek is the boyfriend, despite only short periods of contact with each of them.
While Meredith's life lingered in the balance after drowning, Ellis flatlined and was unable to be revived. And though her relationship with Meredith hadn't always been strong (she told her daughter that she was just "ordinary" after finding out about Derek in her one day of lucidity), everything was set right and Meredith's feelings were fine with her mother's death when, as Meredith was hanging between life and death, she saw her mother's spirit who told her she was "anything but ordinary." She was later cremated, put into a beautiful urn, and for a time was "hanging out in the back of Meredith's closet." Her ashes were later washed down a surgical sink at Seattle Grace Hospital by Meredith and Richard, who saw it as a fitting tribute for her final resting place to be so closely associated with the hospital which she dedicated her life to.
During her residency, she had an affair with former SGH Chief of Surgery, Dr. Richard Webber, when they were both residents. As residents, the two doctors had a defining moment in both their careers and their relationship when they took care of one of the first patients diagnosed with G.R.I.D. (Gay-related immune deficiency, an early name for AIDS).
She was married about 30 years ago to Thatcher Grey, who left the family when Meredith was young, partly as a result of Ellis' affair. Ellis and Richard planned to leave their respective partners and get married but eventually Richard chose Adele over Ellis, although he did still have feelings for her.
Ellis decided to slit her wrists in front of Meredith and forbade her to call an ambulance. When her mother passed out Meredith rang an ambulance and her mother lived. Years later with the help of her psychiatrist Meredith realised that her mother wasn't trying to commit suicide. she cut her wrists in the hopes that Richard would find out and take her back. However, Richard never heard about the incident and she was too stubborn to ask.
After her divorce with Thatcher and break-up with Richard, Ellis moved with Meredith to pursue a postion at Boston General. Her distinguished career included tenures at the Mayo Clinic and for the U.N., and she is noted for pioneering an operation called the laparoscopic Grey Method and won the Harper Avery award twice.
She has also documented a significant aspect of her surgical training, in the form of videos, which were watched while the group were still interns, and in her journals, writing about her relationship with Richard and her surgical training, referencing staff at Seattle Grace, such as Margaret Campbell, and which Cristina greatly enjoys, for both medicine and romance. According to her journals, the decision of whether or not Ellis would get the first solo surgery was the greatest and most terrifying moment in her life.