Welcome to Just Answer and thanks for your question. I'm sorry it has taken so long to get any response. Do you know for a fact that Lillian did not marry a second time?
Do you know her middle name? I found a Lillian A. O'Leary 1893-1990 but she didn't die in New York.
Thanks for the additional information.
In the 1930 Census for New York, Queens (districts 1-250), Enumeration District 66, there is living atXXXXXa Lillian O'Leary, age 37 F, head of house, born NY, both parents born Irish Free State. Also in the household is her son George J. O'leary age 10, born NY, both parents born NY. This would indicate that she lived until at least 1930 when she would have been 37.
The Social Security Death Index has Lillian O'Leary b 11 Aug 1893 d 11 Mar 1990 in Waterville, ME. This was the Lillian A. O'Leary I mentioned.