Did Jane Austen disapprove of people like Marianne?

Sense and Sensibility was the second novel Jane Austen (1775-1817) undertook as an adult. She wrote it in 1797 when she was twenty-two years of age and rewrote it until its publication in 1811. In her juvenilia, written during her teen years, she inaugurated the persona of Marianne in sketch form in her short works like "Love & Freindship [sic]" and "Frederic and Elfrida."
While Austen's adult satire matured along with her ability to understand other people's propensities and temperaments, the early satire in her juvenilia was more directly scathing and made it clear that she discredited women taken up in the extravagant emotionalism of romanticism, as is evident in this sample of indirect characterization of Laura, writing to Marianne, in "Love & Freindship."
"Oh! Heavens, (exclaimed I) is it possible that I should so unexpectedly be surrounded by my nearest Relations and Connections?" These words roused the rest of the Party, and every eye was directed to the corner in which I sat. "Oh! my Isabel (continued I throwing myself across Lady Dorothea into her arms) receive once more to your Bosom the unfortunate Laura. Alas! when we last parted in the Vale of Usk, I was happy in being united to the best of Edwards; I had then a Father and a Mother, and had never known misfortunes—But now deprived of every freind but you—" ("Love & Freindship [sic]")
While Austen's satire matured, her disapproval of the extravagances of romanticism remained constant. Though she developed Marianne as an authentic, complex character with an intricately wrought psychological make-up, she uses Marianne's remarks, opinions and actions to illustrate the dangers of the romanticism she embraced:
Before the house-maid had lit their fire the next day, or the sun gained any power over a cold, gloomy morning in January, Marianne, only half dressed, was kneeling against one of the window-seats for the sake of all the little light she could command from it, and writing as fast as a continual flow of tears would permit her. ... [S]he put all the letters into Elinor's hands; and then covering her face with her handkerchief, almost screamed with agony. Elinor, who knew that such grief, shocking as it was to witness it, must have its course ...
After Marianne's near-fatal illness at the Palmer's estate of Cleveland, Austen uses Marianne's conversation with Elinor to impugn Marianne's previous position. Marianne's own words—now that we have traced her life and witnessed the folly originated in her false beliefs rooted in romanticism—attest to the falseness of her position.
"I cannot express my own abhorrence of myself. Whenever I looked towards the past, I saw some duty neglected, or some failing indulged. Every body seemed injured by me. [...] I have nothing to regret—nothing but my own folly."
The conclusion to be drawn is that, while Marianne is a very vibrant character, Austen disapproves of the sort of life choices, and philosophical and ethical grounds that make her up. Austen disapproves of people like Marianne because of their dependence on the persuasions of romanticism.