My girlfriend is taking me out this sunday, Gift question?

My girlfriend is taking me out this coming Sunday night. Now, we don't get to spend to much time together because we work completly different schedules (I'm weird, I work the graveyard shift, 9pm to 5 am) but have off on this Sunday night since she's taking me out.

She wont tell me where exactly, just that it's in the evening, and I need to wear a suit. She also said that she will be dressing up too.

Now to my question. Since she's scheduled all of this, she's insisting on paying (wont even let me try to help), and everything, I was thinking about giving her some kind of gift on that night... Would a nice corsage to wear on her wrist, or maybe some other flowers to have at her house?

I don't know, any nice, romantic type gifts would be great... Something for her to have at home, or to take with us would be fine, but something romantic is the important thing...

Oh yea, and I'd like to keep the cost to under $100 (US Dollars) if possable, but can go a little above if we need to.