As far as your gf and costuming. My advice, drop it. If she's not interested, then pushing it will make her resent it and you. Now if you see her show interest in a different aspect of costuming then suggest you help her, but don't push an idea on her, let her decide.
For example, if she seems interested in SuperHeros, then you might mention, "Honey, you seemed to like my bat mask, would you be interested in my working on you an outfit while I work on that? If so, which one would you be interested in?" Most importantly, DON'T try to talk her into a skimpy one. It's better to have a girl with a Batgirl costume who likes dressing up, than one who is dead set against costumes because "all you want is for me to wear some skimpy Wonder Woman outfit". (replace Batgirl and Wonder Woman with ANH Leia and Slave Leia for you SW geeks)