4
You gotta hate that...
Keep in mind that unless she is using Windows XP (assuming she is using Windows given here tech background) it is more than likely she'll be using IE 5 which was included as standard with Windows 98 Second Edition, Windows ME and Windows 2000.
Another way around would be to have a look at your webserver log files, as they might be loggin browser type, or you could also install something like PHP-Stats which would track OS, browser and screen resolution stats for you.