She didn't invent dub step and she didn't make it popular BUT Britney DID make it mainstream and brought it to mainstream radio. After she released HIAM and TTWE, both of which have dubstep breakdowns, so many artists started including dubstep breakdowns in their songs and many songs on mainstream radio had it.
Well if anything she furthered the bubblegum pop trend. Everyone wanted to look like and sound like Britney after BOMT and OIDIA....She became a standard for the perfect pop girl
Britney did brought dubstep to mainstream.
Katy did trap
Taylor did country-pop
Beyoncé did the sing-talk thing, which isn't a genre per say but still.