Conversation so far:
When was the role cast?
Eileen Davidson originated the role of Ashley Abbott in June 1982.
Who got that role?
Eileen Davidson.
Did she stay for the duration of the show?
Eileen Davidson originated the role of Ashley Abbott in June 1982, until her first exit on December 2, 1988.

Question: who replaced Eileen?
Self-contained rewrite: who replaced Eileen Davidson in the role of Ashley Abbott?