In order for a women to get rid of that hair and any hair on her anal area she need a brazillian bikini wax. I'm sure it looks great(porn star look) but it is extremely painful, so the chance of you seeing it that smooth is probably slim to none.
If she's shaving her pussy, there's no reason she can't shave the rest (perennium and ass). Maybe she doesn't even know it's there. Mention it to her nicely...how nice her pussy is shaved and that you'd love to see her go all the way back too.
If she was my girlfriend I know for sure I would ask her to shave her PERENNIUM!! But we only had sex once....if we gonna have sex more often I just might ask
or I just buy her some wax maybe she'll gets my point???