How about this. It takes some preparing but I think it's worth it;
You take her on a surprise all inclusive vacation to a sunny place at a resort at a beach. Because you love her and liked to surprise her. It doesnt even have to be expensive. Turkey for example is a very cheap country, most hotels are 5 star all inclusive, at the beach and EVERYTHING is taken care of. Cocktails and food is available and will be served to you anytime you want, while you're sunbathing on the beach.
On the 3rd day or so after relaxing for the first 2 days, say the hotel has an 'treasure hunt' arranged and you'd like to try it. There is a map, you have to follow clues etc. Then, as you approach the X spot, you both start digging and take out the treasure. You open the box and there it is! A beautiful princess cut diamond ring, carefully picked out by yourself back home. You get on your knees for her and propose!
as she sais yes, you kiss and hug and walk her down to this all set up table ON the beach with a candle and a bottle of champagne. It's sun set, you drink and have some appetizers and celebrate. Then, you take her back to the hotel for another surprise. A Gorgeous gown is in a big surprise box, ready for her, you tell her to open the present and when you both showered and got dressed you take her out to the most excellent restaurant in the island. There, you celebrate again in style.
........................
..sigh..................
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Oh yeah, and then you guys get back to the hotel.
After that it's exploring the island and enjoying the luxury and pampering. Until you guys get back home, tell all your friends and family and the whole celebrating starts all over again.