I find myself asking what the harm really is in her actions. Samgirl2, others have made the same suggestions that popped out for me, but the underlying question is why her act bothers you. If it has no professional impact on your interactions with her, then it makes no difference what mask she puts on in her blog posts. She's living a fantasy life but if it makes her happy and doesn't actively harm those around her, why worry about it?
"Unlike men, who really do not care about this kind of stuff, the lady in question then gets a lot of flack from the other women in the workplace for being "fake" or "Female Dog" or "manipulative"."
Many men do indeed care about this sort of thing. Putting on airs isn't solely a female concern by any means, and I've run into lots of fellows who shot themselves in the foot professionally by trying to act fake.
"I wonder whether her superiors realize what a poseur this woman is; it's not going to help her professionally."
Truth be told, unless it's having a deleterious effect on her work just playing at being a social butterfly/fashion maven isn't so likely to blow up on her. The real effect will be in the difficulty she may have cultivating workplace friendships, and that can really bite one in the tail when it comes to promotions or perks.
"There's an expression "dress for the job you want, not the one you have." Its generally considered sound advice... although sometimes to the people around you, they wonder "why is she dressed like that when she's just a lowly [whatever]?" Other people will sometimes advice "fake it till you make it." Again its often touted as good advice.
It sounds like your boss is projecting the life she wants, not the one she has. She might not be there yet with a glamorous life, heck she never may get there. But by projecting herself this way she's a heck of a lot closer then if she just gave up and dressed like a dowdy overweight middle aged woman in a go-nowhere life."
This reminds me of a comedian, who said, "My boss told me to dress for the job I want, not the job I have. So the next day I showed up in a Cubs uniform." The funny part is that this strikes close to this woman's actions, in that she wants to be a fashion plate so she saves her money to buy the big brands and acts the part. WillyNilly's second paragraph sums up my thought on it pretty well, again assuming that it doesn't affect her work. There are those who have labelled it sad, but I'm left to wonder if it's not just as proper to label it oddly empowering. Is what she's doing really all that different from many people who take on a role for public consumption? Heck, Andy Kaufman made a life out of this sort of thing and everyone considered him a genius for it.