So in love is Marianne, that she abandons all her common sense. When Willoughby offers her a horse, she immediately accepts, not taking into account all that goes into the ownership of a horse. And even when the sensible Elinor points out the complications of accepting such a gift, Marianne is "most unwilling to comprehend all the unhappy truths which attend the affair".
When Willoughby suddenly and abruptly leaves the Dashwoods and goes to London, Marianne is heartbroken and shows her sorrowful emotions quite freely. Being the emotional girl that she is, "Marianne in all probability not merely giving way to violent sorrow as a relief, but feeding and encouraging it as a duty". She mopes around, doesn't eat much, and cries a lot. She thinks it would be "very inexcusable had she been able to sleep at all the first night after parting from Willoughby". Not only does she feel genuine sorrow on Willoughby's departure, but she also thinks it's her duty to feel that way.
Marianne knows how much her sister likes Edward Ferrars. But Elinor acts differently around him than Marianne acts around Willoughby. She remains composed and keeps her thoughts and feelings to herself. She notices that when Edward comes to visit at Barton, he is not himself, but she says nothing and doesn't obsess and worry over it as Marianne would. And when Edward must take his leave of them, Elinor remains calm and unemotional. She busies herself with other matters and doesn't shut herself off from the family. But Marianne doesn't understand her sister's lack of concern, for "such behavior as this, so exactly the reverse of her own, appeared no more meritorious to Marianne, than her own had seemed faulty to her".
Elinor again shows her calm rationality when she hears of Edward's secret engagement to Lucy Steele. She is angry and saddened but quietly listens to all that Lucy tells her regarding the engagement. Afterwards, she carefully considers all that Lucy has told her, and she endeavors to discover more by engaging Lucy in private conversation once again. Elinor cleverly and carefully extracts from Lucy the information she wants to know. Unlike Marianne, she doesn't fly into a passion over the matter but ponders in her heart all that she has recently learned.
Marianne can't stand Mrs. Jennings, but when Mrs. Jennings invites the Dashwood sisters to town with her, Marianne immediately declares she will go and that she can easily put up with the woman. However, her only desire and goal, is to be closer to Willoughby. Elinor cannot ignore the "rapture of delightful expectation which fills the whole soul and beams in the eyes of Marianne". Marianne is very much excited about seeing Willoughby and doesn't try to hide it. But tremendous is her grief when Willoughby ignores her and then acts as if he had never had any affection for her. His cold-hearted note to her breaks her heart and for many weeks she is sick with grief. She, somewhat selfishly, refuses to participate in various affairs with Elinor and is sad and downtrodden. She doesn't leave the house for several weeks, both because she has no desire to seek amusement and because she doesn't want to accidentally run into Willoughby. So sensitive is she that she wallows in her grief for a long period of time before beginning to return to herself.
When Elinor and Marianne meet Mrs. Ferrars, she is quite rude to Elinor and very nice and polite to Lucy Steele. But Elinor refuses to be bothered by it, for it is not in "Mrs. Ferrars power to distress her by it and the difference of her manners to the Miss Steeles only amuses her". However, Marianne will not stand for this, and she honorably defends her sister against the subtle remarks against her. "Urged by a strong impulse of affectionate sensibility, she moved to her sister's chair and said 'Dear, dear Elinor, don't mind them. Don't let them make you unhappy'''. At which point she bursts into tears. If their roles had been reversed, Elinor would have sensibly defended her sister by steering the conversation to another point, instead of retorting back and then becoming overwhelmed with emotion. This is a perfect example of how the two sisters are so different. While Elinor bears the criticism silently and calmly, her sister must react passionately.
Fanny is quite distressed by the news that her brother Edward is going to marry Lucy. Being related to her, Elinor sees it her duty to go and see how she is doing, even though she can't stand the woman. This is typical, practical Elinor, dutifully doing what is right. Marianne, however, who is "not contended with absolutely refusing to go herself, is very urgent to prevent her sister's going at all". Marianne doesn't see the point of visiting a woman whom she despises, be she relative or not. Again, Marianne is following her emotions and sensibilities rather than her duties and common sense.
At Cleveland, Marianne again abandons her senses by walking around in the damp and cold and then sitting around in wet clothes and shoes. As a result, she becomes quite ill. Elinor is very worried about her, but keeps her head and dutifully attends to her sister night and day. While Marianne is ill, Willoughby unexpectedly shows up. He tells Elinor all the particulars of why he broke Marianne's heart and how much he regrets what he had to do. He begs forgiveness and asks Elinor to tell Marianne the whole story. Elinor doesn't cry for her sister, as Marianne would have done, but she does feel a little more compassionate for Willoughby.
At the end of the novel, there are two instances when the sisters reverse rolls, when Marianne acts as Elinor would and vice versa. Upon finally returning home to Barton, Marianne tells Elinor that she is finally at peace with herself and can move on and forget Willoughby. After hearing what Willoughby told Elinor, she can finally leave the past behind and forgive him for what he did. This is the kind of sensible action that we would normally see in Elinor. But just as we see a little sense in Marianne, we also see a little sensibility in Elinor. She had been struggling for quite some time with the distress of Edward's engagement to Lucy. But Edward visits Barton and informs the Dashwoods that Lucy has married his brother Robert and that he is no longer engaged. So incredibly happy is Elinor, that she runs out of the room, "and as soon as the door [is] closed, bursts into tears of joy, which at first she thought would never cease". This is just as Marianne would react in such a situation. This proves that though the two sisters are very much different in their thoughts and actions, they are also very much the same.
Marianne Dashwood is a sensitive, emotional, and compassionate girl. Elinor Dashwood is a practical, rational, and sensible girl. These two sisters each have their own personalities, all their own. As a result, the two girls are good complements to each other. Elinor's sense balances Marianne's sensibility. And while Marianne will always be the sister with the strong sensibilities, and Elinor will always be the sister with the strong sense, they will always have a little bit of the other sister in themselves.
