I think that Helena is a very vain, very self-happy (is that a word?) person. She clearly thought herself higher than everyone else. I also see her as a jealous girl. Apparently she nearly had it all. Good looks, riches etc. But she didn't have her mother's knowledge and intellegence and so she stole the diadem.
Helena probably thought herself too high for the baron, after all, she did turn him down although he apparently was head over heels in love with her.
I don't think that Helena's father was either Godric or Salazar. I agree that Ravenclaw was Rowena's husband's name. However, if we are going to be romantic (:P) I think that Salazar is Helena's father. If Godric had been her father he would probably have stepped up and married Rowena, in order to save her virtue. Salazar was probably a frightening and violent person (from what we know). It wouldn't surprise me if Rowena was too afraid to tell him that she was pregnant with his child. Or perhaps she did tell him and he washed his hands of her. (Another reason for him to leave Hogwarts!!!)