Until the late 17th/early 18th centuries, elite European women socialised in predominantly domestic environments - their homes and the homes of their friends/family. In which instance, they would retire to a discreet room and use a chamber pot, which a servant would then take away and empty in the cess pit of the house. Going into the 18th century, many grander townhouses boasted an earth closet, which was a kind of simple toilet which flushed waste into a well of clean soil, rather than water. The flush toilet as we know it today, with a pan of water in a bowl, was patented in the 1770s by Joseph Bramah, but tended to be the preserve of the rich.

In a diary entry from 1664, Samuel Pepys noted that "news comes my Lady Sandwich was come to see us, so I went out, and running up (her friend however before me) I perceive by my dear Lady blushing that in my dining-room she was doing something upon the pott, which I also was ashamed of, and so fell to some discourse, but without pleasure through very pity to my Lady". That is to say, she was ushered into the nearest empty room by the servants, which happened to be the dining room, to use a chamber pot, and was accidentally discovered there. Presumably it was less of a breach of etiquette to stay and talk as if nothing was happening, than to walk back out of the room!

Going into the early 18th century, with the linked developments of the bourgeois public sphere and commercialised leisure, more European women were socialising in places like theatres and pleasure gardens. Cloakrooms and retiring rooms would be made available, so that a chamber pot could be used in some privacy, and larger establishments such as Vauxhall Gardens had dedicated female privies, although these were rumoured to be so unpleasant that a discreet bush in a dark corner of the garden was supposedly more preferable. A special type of chamber pot, known as the bourdaloue, was popularised in France for female usage, and was convenient for travelling and for going out in public - this example in the collection of the Getty shows how its shape was optimised for women http://www.getty.edu/art/collection/objects/5724/chantilly-porcelain-manufactory-chamber-pot-bourdaloue-french-about-1740/.

Edited to add: this painting by Boucher shows a bourdaloue in use. Even allowing for some artistic licence in the interests of titillation, we can see how the woman is able to use the device quite easily. https://commons.m.wikimedia.org/wiki/File:François_Boucher_-La_Toilette_intime(Une_Femme_qui_pisse),_1760s.jpg