SOLVED. YA about a girl at a boarding school sometime between 1890-1910, who tries to keep an unfashionable girl from making friends with her. [s]

[Jasmíne]

The book is about a girl who is orphaned & sent to a boarding school of sorts. After she attends for a while, a new girl comes (I think her name is Fanny). She is very unfashionable and the other girls make fun of her oversized yellow bustle, but the protagonist secretly likes clothes. She writes a journal entry about how strange the new girl is.
Fanny is always friendly to the protagonist, & the protagonist secretly likes Fanny as well, but refrains from showing it in front of the other girls. Fanny tells the protagonist something personal about herself, & the other girls find out. Fanny thinks that she told them her secret & is cold to her from then on. The other girls then find the protagonist's journal entry & take it, add the words "I hate her" at the end, & give it to Fanny. This causes her to leave the boarding house. The story ends with the protagonist writing a letter to Fanny saying that she is sorry, that she actually liked her, & that she didn't write the words at the end of the journal entry.
I read this book sometime between 2007 - 2010

[Ayshe]

Maybe Finding Hattie by Sally Warner?

[Jasmíne]

Solved
Correct Title is "Finding Hattie"