The link doesn't work since I do not have an account with ancestry, however, I know which record you are talking about. I am almost 100% that that is my Mary Hamilton because she is listed as a decorator and my family has said that she dabbled in designing lamp shades. I found her in a 1910 census listed as a lamp shade designer and being a widow meaning that William probably died before 1910.
I do not think that William and John CROWLEY are the same person. Mary and John married in 1893 and then it is said that her and William married in/about 1898. My guess is that since Mary's son John, who was the son of John CROWLEY, was using the surname HAMILTON she wanted it to appear as though William was the father. From what it seems like, John Crowley might not have been so good to Mary and maybe she wanted to disassociate herself from him as much as possible. I know that census records are sometimes off a little bit so that is what is running in my head right now to make sense of that record.
Mary's mother was born in Scotland and I believe that record says Ireland. I have seen errors like that several times so since the rest of the information is correct, I am thinking that is the correct Mary and William HAMILTON.