I posted this in the box office thread, because that’s where the post I’m replying to was, but since it’s about the movie and not the box office take, I figgered I’d bring it here:
First, you are misremembering his line; it was “I’m gonna be honest; I forgot you were still here”. He doesn’t “keep on forgetting” that she’s on his ship; she’s just last night’s hookup that hasn’t left yet. She’s there to establish that Quill is a Lothario; that’s all.