We can't proofread or correct sentences here, but if you will provide the complete sentence (instead of just the phrase you've posted) and explain the situation in which you'd use it, we'll be happy to help with a question about a word or phrase that you think might be incorrect.
sorry about that. This is my own sentence which I am describing a girl who is wearing a red peasant blouse in a picture. However, my English teacher, who is non-native, told me that my sentence was not correct. However, I read a sentence which is "people in ragged clothes with outstretched hands" from an English storybook "The house that Jane built", so I just copied the same sentence style. Therefore, I don't know why it is wrong.
It’s not clear what your teacher meant was wrong with your phrase, as there’s nothing wrong with it grammatically. But it is not a sentence. It’s just a phrase – describing a child but implying (since it starts with “This”, which normally identifies a specific person) that we should already know who she is and/or you have more to say about her.
It's impossible to say for sure why your teacher told you your sentence was incorrect; you would do best to ask him/her. If the assignment was to write a complete sentence, "This adorable little girl in a red peasant blouse" would be incorrect because it is not a complete sentence. (It lacks a verb.)
The only similarity I can see between your phrase and "people in ragged clothes with outstretched hands" is the use of "in" to refer to wearing clothing, and there's nothing wrong with that. "People in ragged clothes with outstretched hands," however, has the problem of an unclear antecedent that makes it sound as though the clothes, and not the people, have the outstretched hands, so it would be wide not to copy it too closely.