Yes, the upgrade version will save her a little money. Compare the upgrade version and full retail version here, http://bit.ly/comparewindows.
Windows 7 will be about the same price wherever she decides to purchase it. If she sees a prices that is too good to be true, it probably is! Make sure she purchases for a reputable retailer or Microsoft Partner to ensure that she gets a genuine copy of Windows - http://bit.ly/genuinewindows.
Microsoft Windows Outreach