Actually, a definitive analysis can be made of Denise...I've seen some of her sheerest garment photos, and her nipples appear to be almost to the side of her breasts, which I've always believed is the primary reason that she doesn't show them off--she fears they would appear too deformed, which I find hard to believe considering our community of boob lovers.
Anyway, what I derive from the supposition that Denise's nipples are so badly "misplaced", for lack of a better word, is the fact that if she had had surgery to be her size, she would most certainly have had her nipples resituated on her breasts, or she's got one helluva lawsuit against whichever surgeon botched her job so badly that she's afraid to show her nipples... 
So, it is what it is. I feel reasonably confident in my evaluations of most models I see to determine for myself whether I believe they are fake or real, and of course, since I am never wrong, I constantly seek to evangelize others who may not believe as I do... 
Q-"Note: that last paragraph was written in self-deprecation"-BE 
I've never had the impression that Denise doesn't do topless because her boobs are 'odd'...
There are several of her photo sets over the years that allow her nipples to be seen under
a transparent bra.
As for nipple placement in general, I've always found it extremely odd that many, if not most, guys seem
to think there is a standard position for them to be...there isn't. Anyone who has studied boobs as much as most of us here, should know this by simple observation. Of course a guy can have a preference, but to say one type is normal and the other is not is pure fallacy. Nipples placed to the side of the breast when seen from the front is a simple formula of size of boobs, size and shape of ribcage and the 'density' or firmness of the breast tissue.
I personally luv the look...what it says to me is that the boobs are larger than they should be for the size of the girl's chest. Look at Darina, pornstar from Eastern Europe as an example of what I mean. I've always found her boobs extremely sexy...I could give other examples. Actually, I will: better known to us is Rachel Aldana...look at her photos from the front: her boobs are so large for her chest, they have no choice but to swell to the sides of her chest.