Actually, I think most of the elves change and grow throughout the series. Cutter changes a lot-- "Chief of Changes" can apply as much to himself as to the times he lives in!
Strongbow has really mellowed over the years-- he has been so often confronted with his own prejudices and so forth, he has been forced to deal with them and come to terms with them.
Skywise has been through a major transition and identity crisis and finally found himself again.
Ember has gone from a happy-go-lucky child to an angsty teenager, and then settled into herself as a chieftess.
As for Leetah, I think one of the most interesting things about her is the conflict between her healer's instincts and her duties to her adopted tribe and her family. She has had to make some very hard choices throughout her life, ever since she left the Sun Village. And I agree that this has changed her outward manner perhaps more than anyone else's in the series. She went from pampered, spoiled center of the Village to wise mother and contributing tribemember in the Holt.