Other variations on Eleanor: - Nell, Nellie, Nelly, Ellie, Helena, Elinor, Lena, Nora (Eleanora).
Have you looked for her in workhouses, hospitals, prisons, police stations or asylums in a later census? Unfortunately some listed inmates by initials. Others had their names but lacked other details, depending on what the person in charge knew about each inmate and how able or willing each person was to provide correct information. Many prostitutes spent time in such institutions. Even if you don't find her in 1851 try a later census in case she re-emerged. Vary your search terms. Try a search with: 1st name + variations, approximate YOB, no surname; add occupation or keyword prostitute, if the search engine allows, and geographical area. Experiment, leaving out/adding pieces of information or changing them. Have you searched for her under surname with no 1st name?
Census enumerators in some places seemed to know all brothels in their area and the women working in them. Others either didn't, or the women hid behind occupations like dressmaker or milliner. To be fair, some probably were genuine dressmakers etc who'd fallen on hard times.
Eleanor may have been living with a man and taken his surname. Hence no marriage.
If she continued her occupation and been arrested, she may have been mentioned again in newspapers.
The woman with whom Eleanor was staying said in her evidence that Eleanor now had her own house. Might that mean she'd become a brothel-keeper herself? She was a bit young, but if the attack had caused permanent damage, it would have been a sensible career move.
Did she have any children?