The 17-year-old from Smiths Falls, Ont., moved up one spot Wednesday after Australian Minjee Lee turned professional earlier this month.
Lee and Aussie teammates Su Oh and Shelly Shin beat Henderson's Canadian team by two shots at the recent world amateur team championship in Japan.
Henderson shot the low individual round at the tournament with 19-under 269.
The runner-up at the U.S. women's amateur championship, Henderson was also the top Canadian and amateur at the Canadian Pacific Women's Open last month.
American Alison Lee is second in the ranking followed by Nanna Madsen of Switzerland.