Preston told People magazine exclusively that she would be unable to take part in the October conference's "Grief & Resilience" panel because she is not prepared to discuss the loss of her 16-year-old son Jett, People.com reported Friday.
"It is with my sincere apologies that I must pull out from speaking at (the) conference. I am sorry, but I truly believed that I could do it," Preston said in a statement. "Otherwise I never would have said that I could. But I am still deeply in the process of healing, and it's just too soon."
The death of the 46-year-old actress' son on Jan. 2 in the Bahamas has been attributed to a seizure.
Journalist Maria Shriver, who is hosting the conference, said in a statement she understands Preston's decision.
"I know how hard it was for Kelly to make this decision and she has my complete support and understanding. Everyone has their own path to healing and their own timetable for grieving," said Shriver, who lost her mother, Eunice Kennedy, and uncle, U.S. Sen. Edward Kennedy, this month.