Ha, finally finished drone minigame with for all my 17 girls. It was not that hard after you learn a trick with traps (you can build 2xN traps and just wait till enemies get inside instead of trying to take free space or splitting them). Last map for last girl had 11 enemies, but I guess even 15 would be fine. It took me just 5 days worth of free tries (22 total) to complete it.