Re: average to plus sized heroines.
This is going to drive me crazy until I google-fu the title, but I remember reading a romance novel where the main character is an average-sized female with "average" looks who doesn't change who she is and still gets the good-for-her Cute Guy at the end. I believe she's a writer who goes on a retreat or something, which is where she meets the guy, and there is at least one other female who is the traditional Hot Girl, but the main character isn't any more than passing envious of her. In fact she just observes everyone else's interactions in the vein of "oh I bet Cute Guy goes for the Hot Girl" not "why can't I be hot like Hot Girl." At least, I don't remember any angst, just that she was a bit matter-of-fact about herself and her less than perfect love life. Turns out Cute Guy is attracted to the main character's personality and finds her beautiful to boot. Shocker!
Also, Amelia Peabody of the Elizabeth Peters' Egyptology series is often described (self-described) as unfashionably proportioned with sharp features, and she placidly resigns herself to a life of spinsterhood* rather than lament or "fix" herself. (* She finds love by the end of the first book but never changes.)