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
Charles Keeler died in 1937.
Jackie Keeler died in 2005.
Leonarde Keeler died in 1949.
Uri Keeler Hill died in 1844.
Joseph B. Keeler died in 1935.
James Edward Keeler died on 1900-08-12.
W. W. Keeler died on 1987-08-24.
Gertrude Keeler died on May 10, 1992, in Los Angeles, California, USA.
Helen Keeler died on November 4, 1981, in Los Angeles, California, USA.
Willie Keeler died on January 17, 1964, in Los Angeles, California, USA.