OK, if it's a feature of the Chrome browser I don't think you can separately disable that - it's just part of the Chrome app, the same as opening multiple tabs or having a back button. All you could do is block Chrome completely, install a different browser that doesn't have the feature and force her to use that.
The drawback is that it's obvious what you are doing in that case, and there are other ways round it if you put your mind to it (just clear your search history, or install another browser which does have the feature, since it's pretty much a standard browser feature these days). But that's all I can suggest.