Joan Gerber
 

Most of the characters were voiced by the same group of people doing different voices so the need for additional voice actors back then was not as demanding. As such Renae Jacobs and Jennifer Darling voiced nearly all of the female characters aside form a couple that Tress McNeil did (neutrinos mostly) and Pat Musick's one off turn as Mona Lisa. I see Joan Gerber a notable voice actress of the past,but cannot assign a character that she did despite her name appearing in the VA credits in at least seasons 3 and 4. Which characters did she voice in the 1987 cartoon?

Aunt Aggie & "additional voices".

She also voiced Shreeka in Shreeka's Revenge.