Strange question but hear me out. I live in a really fun and funky part of San Francisco. We have people staying with us all the time from visiting family to friends who live in the 'burbs and don't want to have to drive home (and yes, some do have kids). If the LW lives in/near a big city the daughter might have taken advantage of the opportunity to go out (and that is why she brought a friend with her). Don't have to worry about DUI (taxi, public transit, walk, etc).

The daughter being horribly rude, taking advantage of her Mom, etc has been discussed (at length) in other threads so I won't comment on it here.

I was thinking of this too. Why else make a "day's drive" (ugh) just to dump the kids at mom's, rather than hiring a sitter? The dad's out of town anyways, and it'd be cheaper than the gas.

Maybe so the neighbors don't see? Messing around on hubby might also explain why she freaked out when mom disapproved- didn't want to get caught.

The big city thing does sound fairly likely though, also would mean the two could have walked/public transported home after drinking.