http://windows.microsoft.com/en-us/windows-10/getstarted-set-up-accounts

Of course, using webmail she can access her mail in a browser you both use in the same Windows account.
And she can have her own favorites if you use different browsers (choose from Chrome, Firefox, Internet Explorer and Bing - although maybe Bing and IE share favorites) even in the same Windows account.

But it's nice to each have his own account.

Kees