Help & advice for modding

Hey everyone. My daughter wants to mod her Minecraft. I did some searching and found a bit of confusion. I have located and opened the .Minecraft folder. In one search, someone said there was a file that should be deleted so mods can work? I could not find that file. I dont wanna mess up her game yknow that would not be good. Version 1.8.1. Which mod loader do I get? Where to get mods without viruses? Any important notes I should know before trying this. Thanks!