And this in a culture where she might as well have said that she didn't want to curtsey to the king.
The odd thing was that her mother kept trying to marry her off to unpleasant old widowers, and she probably couldn't have married without her mother's leave. Yet it kept returning to objecting to marriage. And not with any fear of childbirth.
Other books I've read had her fear domestic tyranny. None of them seem to doubt that avoiding matrimony was the way to pull that off. As if your mother didn't keep you under her thumb. As if your stepmother was not a real possibility. As if your sister-in-law couldn't be as much a pest as any husband. At least you would be mistress of your own household. (One reason why clergy fought tooth-and-nail against the law allowing you to marry your dead spouse's sibling was that a lot of unmarried Victorian women had to take refuge with their married sisters, and they did not want the master of the house to think she was sexually available.)
Nor do these heroines ever considering a living mother-in-law to be a liability. All right, they probably won't face Sleeping Beauty's mother-in-law, who, you may not know, tried to have her two children and Sleeping Beauty herself killed so she could eat them. Or the mother-in-law in Six Swans, who kidnapped her grandchildren at birth and smeared her daughter-in-law's mouth with blood so she could claim she killed and ate them. Still problems less drastic than that could be unpleasant.
To be sure, there were eras in which people would try to evade marriage. Women were less able to evade than men -- but then, a lot of pressure could be applied to men, too. Plato in his Laws discusses the proper way to enact laws, the better sort using both influence and force, by justifying as well as prescribing penalties.
The laws relating to marriage naturally come first, and therefore we may begin with them. The simple law would be as follows:—A man shall marry between the ages of thirty and thirty-five; if he do not, he shall be fined or deprived of certain privileges. The double law would add the reason why: Forasmuch as man desires immortality, which he attains by the procreation of children, no one should deprive himself of his share in this good. He who obeys the law is blameless, but he who disobeys must not be a gainer by his celibacy; and therefore he shall pay a yearly fine, and shall not be allowed to receive honour from the young.
That there should be a law requiring men to marry he takes for granted.
Even when there were no laws, there could be plenty of pressure.
As fast as thou shalt wane, so fast thou growest
In one of thine, from that which thou departest;
And that fresh blood which youngly thou bestow'st
Thou mayst call thine when thou from youth convertest.
Herein lives wisdom, beauty and increase:
Without this, folly, age and cold decay:
If all were minded so, the times should cease
And threescore year would make the world away.
Let those whom Nature hath not made for store,
Harsh featureless and rude, barrenly perish:
Look, whom she best endow'd she gave the more;
Which bounteous gift thou shouldst in bounty cherish:
She carved thee for her seal, and meant thereby
Thou shouldst print more, not let that copy die.