Perhaps I chalk this up to differences in mindset. I don't care about flirting. If my SO flirts, I really don't care. I know he's with me at the end of the day, so that's all that matters. Clearly it wasn't enough for her. And I don not mean that as a shot, but as a statement. But the fact is, if you're secure, he can flirt all he wants, she knows he's going to bed with her that night.