So glad this post helped!
Honestly, as a female, more than anything imagination really helps. Cliches are cliches because they happen all the time. Driving out to a remote location to watch a meteor shower with a bottle of wine and a blanket, going on a sunrise hike...I don't know. Anything that you know she would like, but that you haven't done before will really go over well. Think outside the box. Even if it backfires, hell, you at least tried something new and different.

Good luck!