What do you mean by "didn't have a heart in her"? do you mean that a heart is missing from her hair-do? I noticed from your pic that she is missing her braid/twist and heart, and bangs, which is odd bc both 1600 cupid and diary cupid have bangs and the braid twist, though 1600 has the heart shape and the diary one has just a loop. Where did you get your doll and did it come with a diary? The 1600 Cupid was/is a Walmart exclusive, and the one that comes w/ a diary was sold lots of places (TRU, Kohls, etc). But no matter which Cupid it is, due to the lack of bangs and braid twist, it seems that the doll was either played with and someone did something to her hair and returned it, or the doll's hair just wasn't manufactured like the rest of them were for some reason.
Ok, so yeah, you have the 2nd edition or re-release of Cupid. Some don't like the hair on her and prefer the 1600 style that is super-gelled up, others prefer the one you have because they don't like gelled-up hair and you can brush her hair and she has a diary, many love the diaries. For what it's worth, your doll has been going for more on ebay than the 1600 versions and appears to be more rare.