That's just luck - some people will get it on the first try, some people will try five hundred times and not get it. We don't know what the drop rate is for her, but considering that the devs have been hyping her as a super-rare no-revivals absolute must-have, and considering that people sometimes don't get the girls from events that last three times as long as this one does, I'm not surprised people are going right to the kobans.

Personally, I got her on battle #8, but that's just extreme good luck. We still have no idea what the droprate is, and the devs have certainly been hyping it...though so far, it seems like they've heavily overpromised. Her stats are only slightly better than other girls at the same affection level, and her first couple of scenes and sprites aren't anything out of the ordinary. She's just like every other event girl, except her affection caps out at 5 stars instead of 3.