Meh, romantic gestures are ususally wasted. If she says no, just leave it. There really are plenty of fish in the sea, and in 100 years whos going to care?
Play the old 'he who cares the least, wins' scenario. It generally works. If she's really into you, she'll ask why you all of a sudden changed into being a p***k. Ignore her a little bit and just blow her off for a bit. She'll come around.
Turn up to meet her with your new girlfriend.. Whom just happens to be her sister? Failing that her Mum. Failing that her Gran. Failing that tell her you've got the clap, and now so does she.
firstly you need a big abandoned warehouse. Then you need to fill that warehouse with all manor of strange machinary that allows it to build and reconfigure rooms. Then you need a big super computer, a cake and a gun that makes holes between things, lets call it a portal gun. By that time you will be thinking with portals an therfore able to to portal into her sisters room and take some pictures. On your non date show her these pictures ::buhahahahahahaha:
Wow, you really are thinking with portals. Thought it might be hard to fire off such a shot unless they bounce off mirrors. Damn, I REALLY want a portal gun now. Err... for legit uses.
Why do I get the feeling bit is going to end up with a permanent "Love and Relationships thread?" (Actually it's not a bad idea, that way we'd keep all this in the same place...)