Gaga has 22m with Bad Romance (5.2m), Poker Face(6.8m), Just Dance(6.6m), and BTW(3.8m) alone.. (22.4m).
What about Telephone, Paparazzi, Love Game, Alejandro, You and I, The Edge of Glory..etc
Beyonce should be in the top selling artist category.... She's sold well over 12.5 albums or is that for certifications? (13 Million to be exact and this was according to Soundscan)
As for the Digital Sales... YAASSS for Beyonceé being the only girl from the late 90s/early 2000s in the top 20.