How did Jane stretch the laws of the time?

I'm not sure about the laws, but Jane Eyre certainly defies the social conventions of her time. For one thing, Jane wants to follow her heart; she wants to marry for love. Marriage in Regency England involved women being treated as little better than items of property to be bought and sold as part of a business transaction. It wasn't called the "marriage market" for nothing. Women, then, were expected to marry into wealth, position, and social prominence. Love hardly ever entered into the equation.
So Jane wants to settle down with someone who will love her. But her autonomy and independence are threatened throughout the story, and she often finds it incredibly hard to stay true to herself and to her principles. For example, she comes remarkably close to marrying the somewhat priggish St. John Rivers, even though she doesn't love him. St. John offers her a life in an exotic, far-away country which she'd undoubtedly find a fascinating experience. But marrying St. John would give Jane one kind of freedom, while at the same time depriving her of the freedom that really matters to her: the freedom to follow her heart.
Even though she loves Mr. Rochester, Jane cannot accede to his request to go and live with him in France. As Rochester's insane wife is still alive, she would effectively be his concubine, and she's not prepared to damage her reputation that way. Jane may defy social conventions, but there are limits. But virtue is its own reward, and eventually Jane's commitment to the dictates of her heart pays dividends. She's finally able to be with Rochester, the man she loved all along, and they live blissfully together in a loving and respectable marriage.