She is in Robbie's class when the show starts. Never noticed her before. IMDB confirms.
https://www.imdb.com/title/tt1440909/?ref_=ttep_ep_10

She and Don Grady were born almost exactly one year apart:

Robbie (Don Grady): June 8, 1944
Classmate (Ronne Troupe): June 10, 1945

Now for a visual aid of the class, focusing on Ronne:

320927

320928320929

320930320931

I left one of the other young women in that last image, showing how both she and Ronne were wearing bangs hairstyles.

I'm reminded of the school crushes I had, several in grades K-6, but then in 7th a girl came over to my school (mine was K-8, hers stopped at 6). And I fell for her HARD, my first major crush: so much time thinking about, dreaming about, looking hoping no one would notice. But I never let on to her that I was crushing, even though we had classes together for the next 6 years or so...! One reason was -- I never started driving alone until I started college at age 18, we had both graduated and she went off -- so taking her on a date during HS wouldn't have been an option.

Yep, those are the images. Thanks.

Ronne was 5 years older than Stanley (Chip). When they were playing freshmen in college, her real age was 25, and Polly was just turning 18 according to the show.

Ronne was 5 years older than Stanley (Chip). When they were playing freshmen in college, her real age was 25, and Polly was just turning 18 according to the show.

?

Robbie (Don Grady): June 8, 1944
Classmate (Ronne Troupe): June 10, 1945

Ronne was 5 years older than Stanley (Chip). When they were playing freshmen in college, her real age was 25, and Polly was just turning 18 according to the show.

Whats her name from Family Affair was something like 20 when the show started and started playing Cissy Davis a 15 year old.