Gurney is correct on te prayers, but "tirewoman" is, as you guessed, a woman who assists at a lady's toilet, i. e. a ladies maid. The OED gives examples from 1615.
Quentin Durward was written in 1823. Any suggested meanings must have been in use at that time. An example from 1709- "Dressed with all the art and care that Mrs Toilet, the Tire-Woman could bestow on her." The last example given, 1867, from Ouida- "To while time away by scolding her tire-woman."

An example given for cockered IS the quotation from Quentin Durward: I have not been cockered in wantonness and indulgence." "To indulge or humour," thus indulged or humored. OED. As I indicated, there are a number of definitions for cock, cockered, etc., in use in 1823. It is necessary to find the one that fits the sense of the phrase in the book.

The Compact Edition of the Oxford English Dictionary, 2 vol. ed. micrographically reproduced varies from $75 to an astounding $250- ridiculous!- since thousands were given out by the Book of the Month Club in addition to normal sales. The 1987 supplement runs $95 approx. They list a 2-vol. 1991 2nd ed. at $235, but- is this just a reprinting of the earlier (1971) volumes??