Can't go wrong with cash in a card!  

Gift-Cards are awesome!  It doesn't have to be impersonal; maybe get one for her favorite store.

Champagne is nice unless there is a no-alcohol policy.

Hey, she's YOUR ATF why ask us?! lol :P

Have a good one,
xo
ScarletJ

Hi there! My very first gentleman brought me some chocolates and I was so very surprised. It was the sweetest gesture, and unless there's an allergy I feel like chocolate, women, and certain activities are always a good combination . I don't know what brands of lingerie she prefers, but I really like Josie you can find it at Nordstrom in a good variety. I would suggest the one in Tyson's Corner if that's doable.

Also, paying attention to specific brands she likes in general is a very nice touch and (I think) will always be appreciated.

meaning something SHE wants.If you're listening  to her during your conversations you should know what that is.

. . . lotsa CASH!

what has two cups and can get pretty expensive?

I once had a guest surprise me with an edible arrangement and on the card a cute message about giving a helping hand on keeping my puppies contained. I later received an e-gift card to buy bras, which was probably the best gift ever! It was thoughtful, tasty, and definitely a surprise! If your lady has larger boobs, might I suggest the same. Shoot, even if she doesn't a nice Victorias Secret gift card would still be cool. Women love bras. Lingerie is cool, but bras are so much better IMO! We wear them every day and they can get costly.
 
I am sure there is something she has said in previous visits that will give you a inkling as to what she likes to do, wear, eat, etc in her personal life. If you can't recall, I am sure asking will do the trick, even though that ruins the element of surprise.

Good luck! And if all else fails, a cash gift should do the trick!