If anyone is only 3 days in Bali, I would recommend a trip to Lovina to watch the dolphins. Partly because of the dolphins but more because of the trip through the mountains. Make sure you stop at the gitgit waterfall and just make some more stops, that's the part of Bali that's still mostly untouched and filled with ancient trees.
Of course any Bali trip should include enjoying a beautiful sunset which is especially beautiful when you go to Tanah Lot, which is also an excellent place to shoot some mouthwatering pictures.
For food you definitely have to go to Naughty Nuri's, even though it's not local food you will have the best spareribs ever in a super relaxed environment. For local food check warung Biku or for more upscale but definitely a super experience try restaurant Merah Putih in Seminyak.
Nightlive wise, I would advice going/staying in Seminyak and maybe visit Mint if you like to go out late, it also can solve you're being alone problem
Anyway, cheers and enjoy!
[ Edit: Sorry, no promos please. ]