Concern for Brother's Girlfriend's Condition

I (19f) live with my parents. My brother (32m) and his girlfriend (she’s either 21

or 22, I’m not totally sure) live in a town about 15 minutes away,

but they stayed with us this weekend for my dad’s birthday. My brother and I aren’t that close,

and I haven’t talked much to his girlfriend, but she seems really nice. She’s close to my

age and goes to the same college as me, so I could actually see us being friends.

(Yeah, the age gap between her and my brother is a little weird, especially when

she’s almost the same age as me, but he’s my brother, so if he’s happy...) Last night,

my brother decided they were going to go out for drinks. My parents were already asleep,