I would rule them out since there is no David listed amongst them. The Anna in the 1901 census who moves to Iowa in 1909 also has a son named David.
Send me a PM and I will send you the entire newspaper article about the marriage. The article indicate she arrived just two weeks prior to the marriage aboard the Lusitania out of Liverpool. I found her as A. Jane Johnston, widow, aged 50, last of Omagh, Ireland; names her brother Charles Speer of Creevan, Omagh as her next of kin at home; bound for her brother-in-law, Ambrose Johnston of Zearing, Story County, Iowa.