My friends boyfriend is acting kinda sus?

I (18F) have a friend (19F) who has a boyfriend (19M) who I also happen to be good friends with, through her, so we often talk alone. Recently he's been saying stuff like "I wonder what would have happened if I'd met you first" or "You'd make a really good girlfriend". I might be overreacting, but it makes me kind of uncomfortable. Even when I try to play it off of as a joke by asking what if he had met another member of our friend group first, he rejects the idea and then goes straight back to commenting about me. He also often compliments me saying that I'm beautiful and smart or whatever, which I am personally uncomfortable with most people doing. But, despite me asking him to stop, he won't.

We've had an issue prior to this where he had said some suggestive stuff to me and another friend, which we immediately reported to this friend. She explained it to us as him just being a sexual and flirty person, so we shrugged it off. Should I tell her again, or should I not risk causing awkwardness?
My friends boyfriend is acting kinda sus?
Post Opinion