As soon as Marianne's leg healed, the private balls began at Barton Hall. Willoughby and Marianne "were partners for half the time; and when obliged to separate for a couple of dances, were careful to stand together, and scarcely spoke a word to anyone else." Marianne was ecstatically happy, but Elinor was lonely, finding no one congenial in the company. Mrs. Jennings was too voluble, and Lady Middleton insipid: "In Colonel Brandon alone, of all her new acquaintances, did Elinor find a person who could in any degree claim the respect of abilities, excite the interest of friendship, or give pleasure as a companion."
One day the colonel asked Elinor about Marianne's dislike for "second attachments." The colonel began to talk about a young lady who greatly resembled Marianne "in temper and mind." However, he broke off suddenly, leaving Elinor under the impression that he was referring to a tragic experience in his past.
On the following day, during a walk, Marianne told Elinor that Willoughby was giving her a horse. Elinor, pained at Marianne's impropriety, told her sister they could not afford to keep a horse or a man to look after it. She also doubted the correctness of receiving such a gift from a man whom Marianne scarcely knew. Marianne replied warmly that she knew Willoughby better than "any other creature in the world" except her mother and Elinor. However, she finally yielded to Elinor's good judgment and explained to Willoughby that she could not accept the horse. Elinor, overhearing their conversation, inferred that the two were engaged. This feeling was confirmed by Margaret's seeing Marianne give Willoughby a lock of her hair.
One evening at Barton Park, when Mrs. Jennings tried to find out "who was Elinor's particular favorite," Margaret tactlessly told the company, "there was such a man once, and his name begins with an F." Elinor, embarrassed, was grateful to Lady Middleton, who changed the subject.
That evening a parry was formed for an excursion the next day to an estate belonging to a brother-in-law of Colonel Brandon.
Marianne and Willoughby seem to be overstepping social rules to a dangerous degree. In the eighteenth century, it was not seen as correct for two people to spend so much time together without being engaged. Marianne's acceptance of the horse, as well as her giving away a lock of her hair — a very intimate item in those times — would be considered promiscuous behavior unless the couple were actually engaged.
Also, in Austen's day, courtesy required that young ladies be addressed as "Miss," followed by their Christian name. Thus even the thirteen-year-old Margaret is addressed as "Miss Margaret" by Mrs. Jennings. Elinor, the eldest daughter in the family, is correctly addressed as "Miss Dashwood." Thus when Elinor heard Willoughby address Marianne by her Christian name, she justifiably concluded that they must be engaged.