AIBU to tell my son he made his sister feel unsafe and uncomfortable?

[Resini]

Hi all, last night for our anniversary DS and DD along with DS’s girlfriend took us out for dinner and to see a show. Afterwards DS and his girlfriend suggested we go for some more drinks, they are both members of a private members club and could take guests so suggested we go there.
DH and I don’t go out late very often and don’t enjoy drinking very much so we didn’t stay too long but DD did.
DD is only 21, she is quite young for her age, has only lived at home, where as DS is 28 and his girlfriend 25. Obviously DD can handle herself and doesn’t need her big brother looking after her but it wasn’t her normal environment either.
Today DD has told us, that both DS and his girlfriend got very drunk and both used cocaine. Now of course I’m not naive they are young adults (albeit professionals DS is a solicitor and his girlfriend works in policy research!) and I know these sort of things happen in professional circles in London.
DD ended up going back to DS’s girlfriends flat to stay the night as it got late, she missed the last train (we are out in Surrey) and didn’t want to try get a cab that far. DD told me she felt really uncomfortable as they also invited one of their friends back to stay at there’s and this friend has been flirting with DD all night, she felt he wasn’t listening to her saying she wasn’t interested and didn’t want to be stuck in the same flat. She says she told DS this and he told her she was being silly and that the friend is “docile”.
DD ended up not sleeping at all, she said she felt on edge the whole time and left very early.
She has asked me not to say anything to DS as it will make her look pathetic, but I’m really disappointed in him, both in the getting so drunk he had to “have a tactical vomit” on the side of the street, using cocaine and not taking into account his sisters safety or comfort.

AIBU to think I should send him a message explaining that he made his sister very uncomfortable and owes her an apology?
I don’t want to be overbearing but I also think the behaviour last night was out of order.

I feel like you’re getting a really hard time on here, OP. I’m surprised at the number of people who say your daughter should be responsible for herself at her age. A woman can feel unsafe and in an uncomfortable situation whatever her age. It’s not on us as women to have to always be the ones to change or defuse the situation. You’ve heard both sides of the story now and it’s difficult to know what the truth is. You can only do your best. I doubt the siblings will go out together again! It seems there are many other issues at play here, not just that one night out. I wish you well.

I think you need to have a conversation with your DD about her safety!
I remember at that age my mum telling me if I ever feel unsafe to call her, day or night… she’d rather be woken at 3am or whatever than something happen to me!… or to get a taxi and she’d pay it when I got dropped off… etc!
As for your son…. A solicitor doing cocaine?!… is he really that dumb? Get caught and he’d loose everything! And sorry but YES …. He’s a druggie!…. VERY VERY dark road !