I think it's pretty safe to say that the searches her parents did were the most benign, having to do with yard work, etc. And they are on the other browser. As were perhaps some of her own searches. I think we can imagine herswere mostly social network type things on both IE and Firefox.
But the logic here is not a matter of the volume of innocent searches outweighing the nefarious ones. It's the fact that searches involving ways to sedate people into unconsciousness in the same context as ways of inflicting bodily harm were all done simultaneously and exclusively on the browser she used and she deleted the entire browser immediately after YM left the house that first night. That shows she realized how they could be utilized to infer guilt even though they were done several months earlier, and at this stage of the game LE had been told her daughter was kidnapped. It was a calculated coverup, imo due to her complete cognizance of what they could represent. If they were that innocent, why would she have even remembered them to begin with, much less immediately wiped them off the computer along with the browser she used to search them?
