2 Answers

She's still alive.

Date of Birth
12 January 1925, Glendale, California, USA

Birth Name
Dorlee Deane McGregor

Mini Biography
Best known for her performance as the nasty, gossiping, greedy and arrogant Mrs. Harriet Oleson on the TV series "Little House on the Prairie" (1974). Katherine (Scottie) MacGregor could not appear in the final feature length episode "The Last Farewell" because she was on a pilgrimage in India.

Before moving to Los Angeles in 1970 Ms. Mac Gregor worked as a stage actress on Broadway, off Broadway and in regional theatre in and around New York City.

IMDb Mini Biography By: Edward J. May & Katherine MacGregor

I could locate no death notice and saw that she is currently 87 years old!