My daughter’s website lovemilk.co.uk ranks reasonably well, and she’s happy with the ranking, but she wants to change the domain name of the website to her own personal name, which she has registered. To maintain her rankings as best she can, is it better to:- Change the domain name of the existing (Wordpress) website and setup a re-direct from the old domain name to the new one. OR Duplicate the website and then when she is happy with the rankings of the new site, to then ditch the old one. Thanks for any help
Redirect is the only way to salvage the ranking. If the old domain contained keywords, you will likely drop in ranking for those keywords. I personally recommend against vanity domains, just because there is a ranking advantage for domains with keywords in them. Duplicating the site is a complete mistake, as Google will likely treat them as one and potentially divide the ranking up between them. The new site won't have the inbound links, so the old site will outperform.
There's an official way to let Google know about the domain change. Do a quick search for "Google Change of Address Tool" and you will find it. It may or may not cause a temporary drop in rankings.
Your second idea of duplicating the first site is a horrible one. Yes, go with the redirecting option.
Don't just redirect the site with a 301. After you have duplicated the site you want to add 301 redirects for each of the individual pages i.e LoveMilk.co.uk/shop to NewSite.co.uk/shop. If you have had the LoveMilk.co.uk for a while and it has built up domain authority you will not want to drop that domain. For the sake of a couple of pounds a year you would definitely want to keep owner ship of the domain. If your daughter has other websites and social media platforms linking to specific pages then those links will not pass on if you drop the domain.