If you're using the same profile, it's IE. If you're using separate profiles, it's the Internet settings in her profile. Internet settings are mostly user specific, letting each user have the amount of Browser Helper Objects (BHO) one can tolerate...
There's a nice little tool called Spy BHO remover, available for free at
http://www.securityxploded.com/bhoremover.php. Run it with administrative privileges to get rid of unwanted BHO's in IE.
One problem with IE is that it used to be very non-standard. The dominating market share of it made page makers code in two different manners, both the standard and the IE way. The code would sniff which version would suit better. Although the new IE versions have become more standard I guess that many older sites offer the non-standard page for any IE version, causing conflicts. There has also been a couple of security certificate issues during the last half year or so, which have necessarily not been properly updated. As has been said, teach her to use another browser.