Yep - you can create a brand-new Outlook email address and Microsoft account directly on the new laptop during the initial Windows setup process. You do not need to create the account beforehand.
When Windows prompts you to sign in with a Microsoft account on the new laptop, select "No account? Create one!" During the account-creation process, Microsoft will give you the option to "Get a new email address." You can then create a new @outlook.com address, which immediately becomes the Microsoft account username and login for the new laptop.
So you do not need to create the account on your existing PC first. Creating it directly during setup on her new laptop is actually the cleanest and easiest approach.
The new account will not be linked to your existing Microsoft account. Microsoft accounts are separate profiles associated with the email address and credentials used to create them.
You also do not need to log out of your own PC. Creating her new Microsoft account during setup on a separate laptop has no effect on your existing Windows or Microsoft account, unless you later choose to add her account to your PC.
More at https://www.pcassistonline.co.uk/HelpandAdvice/initial_setup_win11.html
If the above response helps answer your question, remember to "Accept Answer" so that others in the community facing similar issues can easily find the solution. Your contribution is highly appreciated.
hth
Marcin