Let us remember what happened to Chaya and why she had to move to live with Gitl. Her parents both died from a highly contagious disease, which meant that the doctors orderered all of their belongings to be burnt to ashes to insure that the disease did not spread. This of course resulted in Chaya being left without hardly anything to take with her. Thus Chaya has to borrow clothes from Gitl. Note that she is going to wear one of Gitl's dresses for the wedding, and also note what Gitl tells Chaya/Hannah and us to help us be aware of what has happened:
You will wear the dress I wore as a child for Shmuel's Bar Mitzvah. He was so handsome--and so nervous. Just like today. It is too bad that your wonderful clothes from Lublin had to be burned along with your bedding, but the doctors said they carried the disease. As you arrived just two days ago, there was no time to make anything else.
This is therefore why Hannah/Chaya has no clothes of her own and is forced to wear what Gitl provides for her.
To sum it up compared to the boring paragraphs above...., since Chaya had the illness,her clothes had to be burned because they could have carried dieseases.