Hello Jessica & Pip!
Even though that profile is an Open profile, you would have to be on the Trusted List and become the Profile Manager to make the change.
To make the change, you go into the edit function and where the name field is Last Name at Birth lists Eleanor; if you have Trusted List and are the Profile Manager, it will have a  button right after it. It would take you to another page that allows you to correct the last name at birth.
I just went in and changed the names in the Current Last Name and Other Last Names to reflect the sequence of her last names. Take a look and see what I did.
If you are interested in fixing this one, go ahead and do a Trusted List request and ask to become a Profile Manager as well and get it completed! Hope this helps both of you, if not, let me know!