It's quite rare to see a shojo maid manga. Maids tend to be there to assist the heroine, not be the focus of the story. I guess that's technically true for this one as well...look, let me explain below.
A TALE OF AN UNKNOWN COUNTRY (Shirinai Kuni no Monogatari), by Natsuna Kawase. First published in 2001 and first published in North America in 2009.
PLOT:
Rosemarie is the princess of a small but impoverished kingdom of Ardela, where even the royal family has to work part-time selling goods to tourists at their castle to get by. To improve their lot, Rosemarie is to be married to Prince Reynol of the far more advanced kingdom of Yurinela. Rosemarie has heard nothing but bad things about this prince, so to find out more she poses as "Marie" the maid and joins Reynol's household. As the two grow closer, Rosemarie starts to worry that she can't reveal her true feelings without offending him and ruining everything.