Happiness is constructed. It is the direct result of actions taken that further your genes’ goals of survival and reproduction.
Blatantly obvious counterexamples include forced reproduction and rape. Less blatantly obvious counterexamples include masturbation and bacon double-cheeseburgers, though these don't apply to your amended version. The fact that we have the capacity to experience hedonic pleasure because it was adaptive does not mean we experience hedonic pleasure as a direct result of acting to increase our inclusive genetic fitness.
It may very well fit the story like a glove, but that doesn't make it any less egregious of a misunderstanding of evolutionary biology. She's hedonically happier, and she seems to have increased her odds of reproducing; direct causality does not seem present. If her amazing new boyfriend is sterile, it isn't really going to change the equation that much.
I'm skeptical of Roissy's claim, but I'm not sure your examples are as obvious or convincing as you seem to think.
Unless I'm extremely atypical (which is possible), it is incorrect to say that superstimulant foods and masturbation bring happiness. They bring contentment, which is different and less satisfying. To the extent that this is a definitional dispute, the happiness they bring is far weaker and far more evanescent compared to e.g. feeling like part of a group, feeling like you've "made a difference", etc.
Next, regarding forced reproduct...
Poignant short story about truth-seeking that I just found. Quote:
The full thing reads like a flash tour of OB/LW, except it was written in 2001.