Your opinion on someone’s appearance is just that, an opinion, and therefore totally subjective. It might well be a widely shared opinion and based on some good evidence but doesn’t make it a fact.Just calling it as I see it, she does look unfit. For someone her age she has let herself go which is why she looks older than her age. She used to be gorgeous years ago (for example in the video someone posted of her taking over Tom's house).
Stating facts is not mean IMHO.
Yes it is a fact she’s not as slim as she was 10 years ago - that can happen for a number of reasons and not all of them are to do with “letting yourself go”, even if some of what we’ve see of Carrie’s habits won’t have helped.
Credit where it’s due, a fact that has also been pointed out is that she trained for and completed a marathon which requires a certain level of fitness.