In a new interview with Good Housekeeping, the 35-year-old actress describes her anguish as a new mother under contract with Grey's and with movies in the time around 2009 and 2010.
She and husband Josh Kelley decided to adopt around that time, but daughter Naleigh arrived earlier than they expected, and Katherine was busy shooting a movie in Atlanta (presumably Killers).
"I would come home angry and frustrated that I'd missed everything with my kid that day," she explains. "I didn't get to wake her up from her nap, or do bath time or bedtime. I'd have to sneak into her room and kiss her when she was sleeping, hoping not to wake her up."
She continues: "I felt like my priorities were messed up. I was putting so much time and energy into just my work, but I was raised [to believe] that family comes first."
Then, after taking a couple "glorious" months on family leave during Season 6 of Grey's, she realized that she wanted off the show for good.
And the rest is history. Or should we say, Izzie is history.
Do you sympathize with Katherine's plight? Or are you still upset she ditched the show? Let us know in the comments below.
Grey's Anatomy Season 11 premieres Thursday, September 25, at 8 p.m. ET on ABC.