Is my bestfriends bf behavior normal ?

My best friends boyfriend every night tells her to go to sleep in a very demanding and aggressive (dominant ?) I guess tone we are roommates so I hear it every night when he tells her in multiple ways to go to sleep it’s usually 10-12am and very late . He yells at her sometimes hits her bottom to go to sleep almost as if she’s a child (we’re both 18) he’s 22 though , It just annoys me so much however she claims it’s no big deal and it just looks abusive to me . She’s an adult being told and actually listens to go to bed every night almost . It’s super nerve wrecking . Not to mention there’s a few more abusive things he does she allows and tells me to basically mind my business I just care but maybe I’m overthinking it