Is there any way you can get to a public library and come in that way? Does she know your s/n already? Well, if you were fixing her computer then you surely know about clearing the history and the cookies and all that stuff to not leave a trail... You could come right out and tell her you come online for anonymous support. If she doesn't like that, you can both go to couples counseling and have it known by another IRL. (Which might not be such a bad idea, anyway.) TC