I assume that since your wife entered on a K-1 visa, that you are a U.S. citizen. This makes a difference because the time limit is different in each case. Spouses of U.S. citizens can apply for naturalization once they have been lawful permanent residents and married to their spouses for three years:
The spouse of a U.S. citizen who resides in the United States may be eligible for naturalization on the basis of his or her marriage. The spouse must have continuously resided in the United States after becoming an LPR for at least three years immediately preceding the date of filing the naturalization application and must have lived in marital union with his or her citizen spouse for at least those three years.
If this doesn't apply for whatever reason, then the general rule for naturalization of permanent residents applies, and she will have to wait five years instead:
An applicant must also reside continuously in the United States for at least five years as an LPR at the time of filing, though the applicant may file his or her application up to 90 days before reaching the five-year continuous residence period.