Hello:
I wouldn't know too much about how the grammar was in VW's time, but instead of
"if she must be accurate"
I would've expected
"if she had to be accurate"
in the following:
... what was the point, she asked, of buying good chairs to let them spoil up here all through the winter when the house, with only one old woman to see to it, positively dripped with wet? Never mind, the rent was precisely twopence half-penny; the children loved it; it did her husband good to be three thousand, or if she MUST BE accurate, three hundred miles from his libraries and his lectures and his disciples; and there was room for visitors.
To the Lighthouse, by Virginia Woolf (part1)
http://etext.library.adelaide.edu.au/w/woolf/virginia/w91t/part1.html BTW, I expected "had to" based on what Swan tells me on MUST: past necessity and obligation
"Must" is not normally used to talk about past obligation (except in indirect speech). This is because "must" is used mainly for giving orders and advice and for making recommendations, and one cannot do these things in the past. "Had to" is used to talk about 'outside' obligation in the past.
I had to cycle three miles to school when I was a child.
I know of course that modal verbs in English are not too strictly related to times or tenses, still ...
Thank you for any clarifications.
Marius Hancu