There's no automatic way to add such a link as far as I know; however you could construct a code snippet for her to use as part of a copy/paste/edit process - provided she's organised enough and disciplined enough to edit it correctly.
The generic format for such a page link is
<a href='http://bloginfo('url')/?page_ID=N&page=n'>your tag link</a>
bloginfo('url') is the root URL of the site
N is the unique ID for the root page that holds the nextpage links
n is the number of the required subpage [each nextpage break creates a new subpage]. The root page itself always has a subpage number of 1, so all subsequent sub-pages number from 2 upwards: you may need to know that to construct previous/next links correctly. In other words the root page would always be
<a href='http://bloginfo('url')/?page_ID=N&page=1'>your tag link</a>
You can extract the ID of a current root page with code using
get_the_ID(); and the number of subpages in it using
echo $numpages; or
print_r $numpages; etc.
Hope this helps.