All perfect praise be to Allah, The Lord of The Worlds, and may his peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
There is no harm for the woman/wife to wear a wig inside her home if her husband allowed her to do so. This is provided that she doesn`t wear it before non-Mahrams (Marriageable men) because it is part of her adornment. It is also a condition that the wig shouldn`t be made of human or impure hair.
In addition, it is lawful for her to seek treatment, even by undergoing hair transplant, and this isn`t considered an attempt to change Allah`s creation; rather, it is seeking therapy to look as she was before.
The International Islamic Fiqh Academy sanctioned hair transplant in case of hair loss. Its resolution No.(173)/2007 stated: "Sharia permits the necessary and needed plastic surgery with the purpose of concealing the defects resulting from burns, accidents, diseases and the like. For example, dermatoplasty and hair transplant for women who suffer from hair loss." And Allah knows best.