"I think she is amazing, and I am going to miss her to death," Ramirez said Wednesday at a party in New York for People En Espanol's "50 Most Beautiful" issue.
"[Kate] is an enormously talented woman, and I think she is so much fun to watch," added Ramirez. "I wish her continued success."
Walsh's character, Dr. Addison Montgomery-Shepherd, is leaving Seattle Grace for a new life in California as the basis for her new show, Private Practice.
Asked about Walsh's real-life plans to marry Alex Young, a production co-president at 20th Century Fox, Ramirez says: "They're lovely people. I hope it'll be a beautiful wedding."
Walsh, 39, announced their engagement earlier this week.
"I'm very proud to be in this business at this particular time, and I just hope the opportunity will continue to come where I can show the world that there are other sizes, other personalities," she said. "Beauty comes in all shapes and sizes."