I adore
Ivy. It's simple, elegant, and matures well. I think your description fits it perfectly, but I'd also add scholarly. I can also imagine a nice girl who also participates in athletic activities and also popular, but not the obnoxious, tiresome and stereotypical popular. More like a girl that everyone knows and likes for her kind personality.
One name I can picture only on a certain type of person (but never use) is
Gertrude. I picture
Gertrude as a bitter woman with a nasty attitude. Blech
Another name I like but can only picture on a particular person is
Poppy. I see
Poppy as a perky, playful girl. Perhaps athletic, but not entirely dedicated to sports. I see someone who is humorous and likes to make people laugh.
Lastly:
Genevieve. Mature, elegant, scholarly
Genevieve. A girl who has all her manners straight, smart, and a ballet dancer. Perhaps snooty and frilly, but beautiful nonetheless. I picture a plain-looking girl but has one extraordinary physical feature, whether it be her lips or eyes or anything else.