I agree with Italy, and you should also consider France. Both are very beautiful and warm places (provided you go during the Summer) with some great beaches and lots to do both outdoors and indoors. I'd recommend you rent a car (which should cost around 50 euros a day if you get something small) and just see the entire country, whichever one you may choose. Exactly where you go within these countries depends on how much time you have, of course.
In Italy, you should spend 3 days in Rome, Florence, Venice and Milan. Rome has many must-see sights, such as the Coliseum and the Vatican, Florence and Milan have a lot of museums and other great sights such as the Santa Maria Novella and the Milan Cathedral (not to mention the great shopping in Milan, which your girlfriend will love), and Venice has its canals and the Piazza San Marco. If you want outdoor activities, you can go on walking tours around Cinque Terre from Florence, and you can also rent bikes and cycle around Tuscany and Rome, not to mention horseback tours of the Tuscan vineyards. If you have time after seeing these four cities, I'd also suggest 3 days in Naples, where you can swim and see the nearby Pompeii (though you could always enjoy the beaches in Tuscany if you don't have time for Naples), 2 days in Turin, 2 days in Genoa, 1 day seeing Verona and Padua and an extra 2 days or so seeing more of Tuscany, such as San Gimignano, Siena, Prato and Arezzo. When you go from Florence to Milan/Genoa, you should stop in Pisa then rather than travelling there on one of your Florence/Tuscany days, as it is on the way. If you do go to Italy, consider starting in Rome (since this is usually the cheapest place in Italy to fly to) and then go Naples-Siena-San Gimignano-Florence-Pisa-Genoa-Turin-Mila... to Rome to fly home.
In France, you'd want 3 days in Paris, 3 days in Marseilles, 3 days in Nice, 1 day on Bordeaux and 1 day on the Loire Valley. Paris is self-explanatory, as it would be criminal to go to France and skip Paris, the city of love. The Loire Valley goes from Paris to Nantes, and is full of old castles you can stop and see. After that, stop in Bordeaux and tour the adjacent vineyards, then go to Marseilles, where you will find many more great sights and outdoor activities. For swimming, you should go to Nice, which is not far from Marseilles but has better beaches. If you have time afterwards, consider a day in Nimes to see the Roman ruins, 2 days in Strasbourg, a day in Lyon, a day in Dijon, 3 days seeing Normandy and possibly 2 days in nearby Luxembourg. If you go to France, fly to Paris, then go along the Loire Valley and keep going to Bordeaux-Nimes-Marseilles-Nice-Lyon-Dijo... to Paris to fly home.
Both countries are very beautiful and cater to your needs perfectly. They are both warm, both have a variety of indoor and outdoor activities, both have some amazing sights and buildings, both have some great shopping opportunities (Milan and Paris particularly), both very romantic, both similarly priced and both you and your girlfriend will have a great time wherever you go, so you can't go wrong. However, both will end up costing quite a bit of money. You will need to hire a car, which at about 50 euros a day will cost around 1,200 euros, you will need to pay for petrol which will cost another few hundred, you will need to cover food and accommodation, which will cost around 100 euros a day/2,400 euros combined (though this will obviously vary depending where you stay/what you eat), there's the plane ticket, and on top of everything, you'll need at least around 1,000 euros for spending money to be able to enter the museums and hire bikes or whatever else you may want to do.
Because of the relatively high cost, I would also like to offer a third, cheaper alternative: Malta. It's not as nice as France and Italy, though still very beautiful, and since it's and island, you won't need a car which will cut out the price of rental and fuel. From Malta, you can also take a ferry to Sicily which I believe costs about 80 euros for a return trip for two (though I may be way off, so double check this, but I know it's relatively cheap). You would not need as much spending money, since all you can do here is lie on the beach, see the odd sight and take an occasional bike ride, and for that reason, you wouldn't stay for more than two weeks (1.5 in Malta, 0.5 in Sicily) because you'd get very bored after a while, thus cutting down your food/accommodation cost, too. Don't get me wrong, Malta is also very beautiful and there is stuff to do, otherwise I wouldn't suggest it. What I'm saying is if you can go to France or Italy, do that. If not, Malta is an excellent alternative.
Enjoy your trip :)
Morocco is a beautiful destination, very interesting, lively and diverse. The romantic city of Marrakech is a good base, you can make lovely trips to the high Atlas mountain, but the city is also fascinating. There are many companies that organize all kind of programs, jeeps, camels, hiking. In Marrakech stay in the historic Medina. Ryad Dyor is a wonderful traditional Moroccan ‘hotel’, with a rooftop terrace offering views on the Atlas, a traditional hammam, but also the modern facilities one needs.
Egypt Cairo and Luxor :) the pyramids and the temples
St Maarten is soooo beautiful and also St Thomas. Go on the carribbean cruise :) www.carnival.co.uk
Italy is beautiful. There's a lot of outdoor sight seeing, and great scenery. I would suggest going with a tour group if it is your first time.
