No.
1. There was nothing about the lives of those that would have come about due to her living that were any less valuable than the lives that Captain Kirk and Mr. Spock knew of. Letting her die "killed" all those people as surely as all the ones they had known had been killed.
2. It may be that no one was killed in any case, and that the alternate just split off so that there were two different futures. In that case, letting her die was a personally selfish choice of "We think we can get back to our time easier if you get hit by a truck."
3. The most obviously glaring defect in the scenario though, was that Edith Keeler had shown herself to be an intelligent woman of great insight and broad acceptance of the unusual. She already suspected that Captain Kirk and Mr. Spock were different. In short, they could have simply told her, "Hey, don't advocate for peace, or Hitler will win and life will be bad." With suitable proof - which they had the means to provide - she would have gone along with that and all would have been well.
Edith Keeler was created in 1967.
FreakyLinks - 2000 Subject Edith Keeler Must Die 1-3 was released on: USA: 20 October 2000 Finland: 27 March 2001
Jackie Keeler died in 2005.
Leonarde Keeler died in 1949.
Charles Keeler died in 1937.
Joseph B. Keeler died in 1935.
Uri Keeler Hill died in 1844.
W. W. Keeler died on 1987-08-24.
James Edward Keeler died on 1900-08-12.
Edith Keeler is a fictional character from the "Star Trek" universe, specifically introduced in the episode "The City on the Edge of Forever." She does not have a historical counterpart in real life; her character was created for the storyline involving time travel and moral dilemmas faced by the crew of the USS Enterprise. The episode explores themes of sacrifice and the impact of individual choices on history, but Keeler herself is not based on a real person.
Gertrude Keeler died on May 10, 1992, in Los Angeles, California, USA.
Helen Keeler died on November 4, 1981, in Los Angeles, California, USA.