Unless we define “radical female suffragists” in a very narrow way, they did not support Jeannette Rankin’s vote against US participation in World War I.
While Jeannette Rankin was unquestionably a female suffragist, that is not all that she was. She was also an ardent pacifist. She believed that violence was never an appropriate response to anything. It was for this reason that she voted against US participation in World War I. In fact, when she was once again in the House of Representatives in 1941, she voted against declaring war on Japan after the attack on Pearl Harbor.
However, it is not true that female suffragists and pacifists were one and the same. Pacifism was not a major aim of the women’s suffrage movement. Therefore, many organizations that were in favor of women’s right to vote were also in favor of American participation in World War I. Proof of this can be seen in this link. Here, we see that suffragist groups wrote a letter to President Wilson before the US was involved in WWI. In that letter, they pledged to help with the war effort if the US did become involved.
Thus, we can see that the majority of female suffragists did not adhere to Rankin’s views on pacifism.