ye thats one of the reasons I argue with her 
she thinks adding stuff is useful, like I use CCleaner never had problems and she wanted to add this other cleaner that is very similar
Well, that's interesting.
Let's leave it to essexboy to suss this one out, and recommend the best way to go on this.
As liubomirwm says, an active resident a/v program is almost always global in installation and not restricted to certain user accounts in operation, as you say is happening here. What that means is that two resident active a/v programs would have the admin permissions and settings to cover the entire Windows operating system and installed programs down to the lowest core levels; neither is restricted in operation in any way. An a/v program has access to everything. So, they would and will clash at some time or other. Potentially a very bad idea (running two of them at the same time) is at the basic core because of this.
A solution to your issue here is to restrict user rights to install whatever or get her another computer of her own. The owner should be the admin and no one else.
