Unfortunately if her husband never became a US citizen she would not be eligible to obtain a green card under the widow self- petition , which allows widow(er) of a US citizen to file for same within two years of the death of the spouse to obtain LPR status. You should seek an immigration counsel with experience to explore other possible ways for her to come to the US, eg, DV lottery, etc. I for one would want to know how the husband obtained his LPR status ??
Mr. Asatrian's practice is dedicated to the area of immigration and nationality law. Please note the information provided herein does not constitute legal advice and should not be construed as such by anyone. It should not be relied upon as legal advice as more specific facts, research and analysis may be required to formulate a proper strategy and action in your matter. Please note this does not create an attorney-client relationship whatsoever. You should seek the assistance of an experienced immigration attorney to review your matter thoroughly and gather all of the necessary information and documentation to provide you with the best possible legal solution.