Take a look at Control Settings, Accessibility
for modifying accessibility options.

If she has complete control of her right hand, I would
certainly suggest getting a five button wheel mouse.
You can see my own settings at
My Notes on Mouse Wheel and Button Settings
http://www.mvps.org/dmcritchie/excel/mouse.txt

Preferably (in my opinion) with button 4 on left side and
button 5 on right side rather than both on same side.

Following Gord's suggestion the use of Shift+F8
might be a better shortcut for your friend for the
wheel button (I have it set to Enter).

You might take a look at these pages particularly at
the identified fragment ids (#...).
http://www.mvps.org/dmcritchie/excel/fillhand.htm#mouse
http://www.mvps.org/dmcritchie/excel/shortx2k.htm