Here are two more short bits of information which provide more insight into the family connections in my O'Brien line.
First is another news clipping on Rose O'Brien which appeared in the Decatur Herald on 24 February 1912. This clipping mentions that she was returning from her older brother's wedding in Indianapolis. The wedding was for my great-grandparents, Harry Edward O'Brien and Blanche Lamon.
The ceremony occurred on 18 February 1912 in Indianapolis, Indiana.
The second bit of information is on Anna Alice O'Brien, Harry's older sister, and their Aunt Anna Maria O'Brien. They appear in the 1905 Wisconsin State Census, in Whitewater, Walworth County, Wisconsin, working as milliners. This answers the question I had previously on the timing of their partnership in Wisconsin.