Make sure that you've got 'All' selected in the filter results boxes to the left of the search results.

Otherwise, it might be that your junk filter's still working. If your sister messed with the junk filter, you might have to click the 'forget training data' button on the junk filter page. Now set the slider to wherever you like it, choose the display junk option that you want & click Apply & ok. Restart LW.