Mapp and Lucia (Mapp & Lucia #4) by E. F. Benson; 1931/2005. Softcover.

Subtly brilliant comedy of social rivalry between the wars. Emmeline Lucas (known universally to her friends as Lucia) is an arch-snob of the highest order. In Miss Elizabeth Mapp of Mallards Lucia meets her match. Ostensibly the most civil and genteel of society ladies, there is no plan too devious, no plot too cunning, no depths to which they would not sink, in order to win the battle for social supremacy. Using as their deadly weapons garden parties, bridge evenings and charming teas, the two combatants strive to outcharm each other - and the whole of Tilling society - as they vie for the position of doyenne of the town.