Meg has a negative experience when she is invited to the Moffats, who are much wealthier than she is. Her clothes don't quite fit in, as they are not as grand as what the other girls have, and Meg has to listen to Mrs. Moffat say that she knows Mrs. March has laid "plans" for the March sisters, implying she is plotting to find them rich husbands. Meg also feels some resentment that she can't afford all that the other girls have.
However, Meg's biggest mistake is allowing Belle to dress her up for the dance:
They laced her into a sky-blue dress, which was so tight she could hardly breathe and so low in the neck that modest Meg blushed at herself in the mirror. ... A lace handkerchief, a plumy fan, and a bouquet in a shoulder holder finished her off, and Miss Belle surveyed her with the satisfaction of a little girl with a newly dressed doll.
Laurie expresses his displeasure and tells her he thinks Jo would not be pleased. Meg isn't at all like herself in the finery, and she overhears Major Lincoln saying to his mother,
"They are making a fool of that little girl. I wanted you to see her, but they have spoiled her entirely. She's nothing but a doll tonight."
"Oh, dear!" sighed Meg. "I wish I'd been sensible and worn my own things, then I should not have disgusted other people, or felt so uncomfortable and ashamed of myself."
Meg has an uncomfortable time at the Moffats, but in the end it has a positive impact on her. She learns the valuable lesson to be herself and not to try to put on airs. When she asks Marmee if she has plans for the girls, Marmee says yes, but not of the kind Mrs. Moffat thinks. Marmee doesn't care if her daughters make fashionable marriages, but her plan is for them to be virtuous, independent, caring young women who will be comfortable and content with whatever economic status they end up in. All of this is a good preparation for Meg to accept the courtship and marriage proposal of the poor John Brooke and to be satisfied with her humbler lifestyle.