Riding on unfamiliar roads at nighttime the boyfriend has probably never ridden a scooter before,add in alcohol and sand on the corner plus inexperience.
Grab a handful of front disc midway around a wet and sandy corner,the bike will literally disappear from under you and faceplant you in the road as has happened here?
An experienced rider will go slower and never use the front disc mid corner,instead and only if strictly necessary using the back brake as that will be a controlled skid but generally no braking whatsoever.