One user account running slow

Hi, I wonder if any of the community can help. Was running OS X Lion on my 2 year old iMac then upgraded to OS X Mavericks a few days ago. Since then have been experiencing slowing down on one user login. My login is fine - internet works at lightning speed. But wy wife's login is now misbehaving in a very strange way. First, when switching user using the fast switch it takes a good 10 seconds for the login box to appear. This only happens when switching from me to my wife's login. Other way round it's as fast as ever. Then once my wife has logged in and surfs on Firefox (version 24) things get slow. Wierdly though Google is really bad for searching - sometimes takes 20 or 30 seconds for search to complete. Yahoo search is okay (still using Firefox) but slower than when running on my login. (How can one website - Google - be slower than another...?). Then if you use Safari on my wife's login it is okay - Google is fine (but still a little slower than on my login). On my login websites load almost instantly but on my wife's - when using Safari it might be about a half to one second longer.

This all happened since upgrading to Mavericks. Any ideas anyone?

AntmanD