Did Ellie Walker come back on the Andy Griffith show show?

You are likely thinking of Ellie Walker, played by Anita Corsaut, who played the role of Helen Crump on the Andy Griffith Show.

Helen Crump did not "come back" to the show after leaving Mayberry to get married to Andy Taylor. She did not appear in any later episodes of the original show.

The show ended in 1968, and while there were some reunions of the cast and a few television movies made in the 80s, Helen Crump was not a part of those.