اَلسَّلاَمُ عَلَيْكُمْ وَرَحْمَةُ اللهِ وَبَرَكَاتُهُ
Islam admonishes Muslim women to dress modestly and cover their 'Awrah and forbid the use of false hair.
Allah says in the Quran in Surah an-Nur verse number 31:
وَقُل لِّلْمُؤْمِنَاتِ يَغْضُضْنَ مِنْ أَبْصَارِهِنَّ وَيَحْفَظْنَ فُرُوجَهُنَّ وَلَا يُبْدِينَ زِينَتَهُنَّ إِلَّا مَا ظَهَرَ مِنْهَا ۖ وَلْيَضْرِبْنَ بِخُمُرِهِنَّ عَلَىٰ جُيُوبِهِنَّ ۖ وَلَا يُبْدِينَ زِينَتَهُنَّ إِلَّا لِبُعُولَتِهِنَّ أَوْ آبَائِهِنَّ أَوْ آبَاءِ بُعُولَتِهِنَّ أَوْ أَبْنَائِهِنَّ أَوْ أَبْنَاءِ بُعُولَتِهِنَّ أَوْ إِخْوَانِهِنَّ أَوْ بَنِي إِخْوَانِهِنَّ أَوْ بَنِي أَخَوَاتِهِنَّ أَوْ نِسَائِهِنَّ أَوْ مَا مَلَكَتْ أَيْمَانُهُنَّ أَوِ التَّابِعِينَ غَيْرِ أُولِي الْإِرْبَةِ مِنَ الرِّجَالِ أَوِ الطِّفْلِ الَّذِينَ لَمْ يَظْهَرُوا عَلَىٰ عَوْرَاتِ النِّسَاءِ ۖ وَلَا يَضْرِبْنَ بِأَرْجُلِهِنَّ لِيُعْلَمَ مَا يُخْفِينَ مِن زِينَتِهِنَّ ۚ وَتُوبُوا إِلَى اللَّهِ جَمِيعًا أَيُّهَ الْمُؤْمِنُونَ لَعَلَّكُمْ تُفْلِحُونَ - 24:31
And tell the believing women to reduce [some] of their vision and guard their private parts and not expose their adornment except that which [necessarily] appears thereof and to wrap [a portion of] their headcovers over their chests and not expose their adornment except to their husbands, their fathers, their husbands' fathers, their sons, their husbands' sons, their brothers, their brothers' sons, their sisters' sons, their women, that which their right hands possess, or those male attendants having no physical desire, or children who are not yet aware of the private aspects of women. And let them not stamp their feet to make known what they conceal of their adornment. And turn to Allah in repentance, all of you, O believers, that you might succeed.
Allah use the word زِينَتَهُنَّ the plural form of زين which means decoration / adornment / that prettify. Note that He does not use the word hair in particular. Thus concludes all kind of decorations to be adored on woman. Which scholars generalize it as 'Awrah (parts that must be covered).
More over, Mu'awiya bin Abi Sufyan and 'Aisya was reported saying that the Prophet (ﷺ) forbid the use of false hair.
These hadith was recorded in al-Bukhari's Book of Dress:
Chapter (83): The use of false hair
Hadith (5932 - 5932)
(Book 77, Chapter 83, Hadith 147 - 153)
A woman came to Allah's Messenger (ﷺ) and said, "I married my daughter to someone, but she became sick and all her hair fell out, and (because of that) her husband does not like her. May I let her use false hair?"
The Prophet (ﷺ) said:
"Allah has cursed the lady who artificially lengthens (her or someone else's) hair and also the one who gets her hair lengthened."
Humaid bin 'Abdur-Rahman bin 'Auf narrated that Mu'awiya bin Abi Sufyan, who was on the pulpit and was taking a tuft of hair from one of his guards, saying, "Where are your religious learned men? I heard Allah's Messenger (ﷺ) forbidding this (false hair) and saying, 'The children of Israel were destroyed when their women started using this.'"
Sa`id bin Al-Musaiyab narrated that Mu'awiya came to Medina for the last time and delivered a sermon. He took out a tuft of hair and said, "I thought that none used to do this (use false hair) except Jews. The Prophet (ﷺ) labelled such practice, (the use of false hair), as cheating."