I found this in an article in the government archives. (I'm sorry that I don't have the link, but I've yet to figure out how to do it on the iPad.) This seems to indicate that your ggm would have become a citizen in 1917 with her husband.
"After 1907, marriage determined a woman's nationality status completely. Under the act of March 2, 1907, all women acquired their husband's nationality upon any marriage occurring after that date. This changed nothing for immigrant women, but U.S.-born citizen women could now lose their citizenship by any marriage to any alien. Most of these women subsequently regained their U.S. citizenship when their husbands naturalized. However, those who married Chinese, Japanese, Filipino, or other men racially ineligible to naturalize forfeited their U.S. citizenship. Similarly, many former U.S. citizen women found themselves married to men who were ineligible to citizenship for some other reason or who simply refused to naturalize. Because the courts held that a husband's nationality would always determine that of the wife, a married woman could not legally file for naturalization.(6)"


