In my case, I got Cupid in the 4th day of the event with more or less 500 battles (w/ energy refills). I'm losing hope, because until yesterday there's still no girl drop. But after few battles (total of 300+ battles), I got Spring Spirit. Few hours ago I'm desperate to get the last girl so I spend almost 2K+ kobans. At last Ishtar dropped. Don't lose hope guys, but honestly this is the most hardest event that I've experienced. Goodluck!