What's the Name of That Book??? discussion

Do you know any chicklit/contemporary/historical /humorous romance about case of mistaken identity, for the heroines part, and she continues to pretend along the way and it takes majority of the book? No spy or anything like that. Maybe a girl is broke and she was mistaken to be the new employee or something.
or books along the lines of: The Undomestic Goddess
really appreciate it XD

You could try Life as I Know It.

There's also stuff like My Father Had a Daughter: Judith Shakespeare's Tale or The Girl She Used to Be (both less likely to be what you're looking for), and if you want total fluff, there are a ton of Harlequins like A Prince of a Guy or Princess In Denim.

Not exactly mistaken identity, but a plot built on the protagonist's lie and carried on through the novel:

L'Amber by Tanith Lee

Surrender to Sin
A Countess Below Stairs
Perdita

The Lying Game

bump...anything else?

I Married a Dead Man. But it's a vintage book and not quite chick lit